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Premium gas...?
The HyHi manual states that it requires at least 87 Octane gas, but higher octane is preferred.
I've been running 87 Octane only, since I'm a cheapskate. I've always understood that if you're not hearing engine-knock, then there's no reason to buy premium gas... But I think this gets more complicated with computer controlled variable timing engines. Does this old rule still apply? And more specifically, is there really any reason to run high octane gas in the Hybrid Highlander? Will it increase my mileage? Will it increase my mileage enough to pay for the more expensive gas? Thanks, _Am |
Re: Premium gas...?
Exaclty how are you being a cheapskate? Higher octane rating DOES NOT mean better gas.
If your car requires 87 (such as mine... HCH I), putting anything higher than 87 is a waste of money and MORE importantly robs the car of performance. Not to mention could damage your engine. |
Re: Premium gas...?
I can't find it online in the forums, but I recall that somebody did their own study to see if the higher octane made a difference in their MPG results. Their conclusion, if I recall correctly, was that there was such a negligible difference that it didn't matter if you stayed with 87 as the owner's manual says or put in "the good stuff".
As other discussions here have said, the main things to be sure to do are (a) keep your tires properly inflated; and (b) use the Toyota-recommended oil -- 5W20 or 0W20... not the 5W30 that's printed on the oil cap. |
Re: Premium gas...?
Can you give a pointer to where toyota recommends 5w20 or 0w20 over instead of whats printed in the manual
\ Thanks |
Re: Premium gas...?
Here is a forum post with a scan of the TSB from March 2006
5W20: This oil has been set as the Toyota genuine engine oil, starting in February 2006 for the US. Series: AZ, GR, JZ, MZ, NZ, RZ, UZ, VZ, 1ZZ-FE, 2TR-FE 0W20: This oil's initial application is in the 2006 model year 2AZ-FE engine and will be used in new engines to be developed. 2AZ-FE Camry, 2AZ-FE Solara, 2AZ-FE Highlander, 2AZ-FE Rav4 (ACA3#) |
Re: Premium gas...?
Originally Posted by chicagoandy
(Post 125394)
The HyHi manual states that it requires at least 87 Octane gas, but higher octane is preferred.
I've been running 87 Octane only, since I'm a cheapskate. I've always understood that if you're not hearing engine-knock, then there's no reason to buy premium gas... But I think this gets more complicated with computer controlled variable timing engines. Does this old rule still apply? And more specifically, is there really any reason to run high octane gas in the Hybrid Highlander? Will it increase my mileage? Will it increase my mileage enough to pay for the more expensive gas? Thanks, _Am However, Toyota has designed the Highlander Hybrid engine with a very high compression engine to take advantage of the properties of premium fuel if it is used. Toyota recommends premium fuel in the owners manual for best performance in the HiHY. Note that using 89-93 octane in the Highlander is optional. Using 87 octane will not cause any drivability problems. If you use premium in the Highlander Hybrid, the engine will be more much more responsive as expected. However, the engine will also run more efficiently when driven conservatively such as when you are driving with cruise control on at highway speeds. The engine actively advances the ignition timing as much as allowed by the fuel grade used under light engine loading and part throttle to maximize fuel efficiency. I have a Scan Gauge II in my Highlander and it digitally displays the engine timing advance every few seconds. I have noted that the engine is at it’s most advanced timing settings when driving down a level highway at 65mph with cruise control on and the engine at a low and stable RPM. 89-93 octane will lead to improved fuel economy if you have the self-control not to use the added reserve horsepower. The other part of the equation is the differential in price between regular and premium. When gas was $2, 91-93 octane was typically $0.20 more or a 10% surcharge over 87 octane. With gas closing in on $4 per gallon, premium is still only typically $0.20 more resulting in a reduced 5% surcharge over regular. Thus the percent cost difference between premium and regular is narrowing considerably as fuel prices rise. This may tip the balance for the premium’s extra fuel efficiency paying off. With a typical 28 MPG for the Highlander, you need to improve fuel mileage with premium over regular by 1.4 MPG to break even. When gas was $2/gallon, A 2.8 MPG improvement was needed to break even. The Highlander Hybrid has a very high compression ratio of 10.8. This predisposes it for higher octane fuels. High compression ratio engines are more efficient than low compression ratio engines all else being equal. However, the higher pressures in the cylinders cause the gasoline to be more difficult to control from a combustion standpoint. Gas will ignite more rapidly at higher cylinder pressures which can result in engine knock if the combustion peak pressure occurs too early in the downward stroke of the piston. Engine knock can damage an engine. Modern engines all have knock sensors tied into the vehicle’s engine controls which operate with lightning speed to retard (delay) the ignition spark timing to head off this knock condition before the driver could ever notice it. This automatic dial back of engine timing and engine efficiency is what allows 87 octane fuel to be used in the Highlander’s high compression engine without any adverse effects. Premium fuel requires higher temperatures and pressures to combust properly and it burns more slowly than regular fuel. Thus, premium fuel behaves more controllably under the higher compression conditions in the Highlander engine and will allow the engine to advance the spark timing more than with regular fuel resulting in higher engine efficiency. The standard internal combustion engine is terribly inefficient. Only about 30% of the gasoline you buy is actually converted into mechanical energy to make the vehicle move. A whopping 70% of the fuel you pay for is just converted into wasted hot air that escapes from the radiator, the tailpipe, and radiates off the engine itself. The engine ignition timing is extremely important in extracting the maximum amount of mechanical energy from the burning fuel. It’s a complex choreography but in simple terms the fuel burn should be timed to reach maximum piston force at approximately 15 degrees of crankshaft rotation past top dead center of piston travel. When lower octane fuel is used in a high compression engine, the fuel burns more quickly, reaching peak forces much sooner than high octane fuel. This potentially causes knock. The spark timing is retarded to reduce the knock but this results in less of the fuel energy being captured by the piston as mechanical energy and more being ejected from the engine as waste heat. |
Re: Premium gas...?
very good post don.
the only variable i don't quite comprehend is the ecu - how 'adaptive' is it? does it follow a standard timing map as written into the s/w and simple advance as much as the fuel in the tank will allow? if we run 5 tanks of 87 and then throw in a tank of 93 will we see timing advanced instantly, or is there a 'learning' period for the ecu to adapt? |
Re: Premium gas...?
Originally Posted by chicagoandy
(Post 125394)
The HyHi manual states that it requires at least 87 Octane gas, but higher octane is preferred.
Select octane rating 87 or higher. Use of unleaded gasoline with an octane rating lower than 87 may result in engine knocking. |
Re: Premium gas...?
Originally Posted by petesell
(Post 126863)
very good post don.
the only variable i don't quite comprehend is the ecu - how 'adaptive' is it? does it follow a standard timing map as written into the s/w and simple advance as much as the fuel in the tank will allow? if we run 5 tanks of 87 and then throw in a tank of 93 will we see timing advanced instantly, or is there a 'learning' period for the ecu to adapt? A corrective ignition timing control function in the ECM makes a final adjustment to the pre-mapped timing settings based on such conditions as engine speed transitions, cruise control operation, traction control activation, knock detection, etc. In simple terms, the corrective ignition timing algorithm for knock retards the timing in relatively quick discrete steps until the knock just disappears. If knock is no longer detected, the ECM then begins to advance the timing again but now in slow discrete steps. If knocking occurs during these slow advance steps, it again retards the timing in quick steps. The engine is most efficient using a particular grade of fuel when the ignition timing is fine tuned to the ragged edge of advance just before knock occurrence. At this setting, the engine achieves the best fuel economy, engine power output, and lowest exhaust emissions. The advance timing correction is not glacial in response. The vehicle should correct for a higher octane shortly after filling the tank with 93 octane but not instantly. |
Re: Premium gas...?
Originally Posted by Don R
(Post 126570)
The other part of the equation is the differential in price between regular and premium. When gas was $2, 91-93 octane was typically $0.20 more or a 10% surcharge over 87 octane. With gas closing in on $4 per gallon, premium is still only typically $0.20 more resulting in a reduced 5% surcharge over regular. Thus the percent cost difference between premium and regular is narrowing considerably as fuel prices rise. This may tip the balance for the premium’s extra fuel efficiency paying off. With a typical 28 MPG for the Highlander, you need to improve fuel mileage with premium over regular by 1.4 MPG to break even. When gas was $2/gallon, A 2.8 MPG improvement was needed to break even. That was a great reply and largely what I was looking for. After reading your post I tried running with 91 instead of 87. I saw an almost immediate, meaningful improvement in mileage. While before I rarely got over 27 MPG, now I can easily get 31. To me, I saw clear and convincing evidence that the Hybrid Highlander will run much more efficiently on premium gas. Some numbers: Cost of regular gas $3.40 premium premium $0.20 With 87 Octane. Best mixed mileage 27 Cost of 100 miles = 12.59 Distance per tank = 464.4 With 93 Octane Best mixed mileage 31 Cost of 100 miles = 11.61 Distance per tank = 533.2 Differences: Running with 93 Octane at a cost of $3.60/gallon vs 87 at 3.40/gallon Saved me $.98 every hundred miles and adds an calculate extra 68.8 mile range. As the saying goes, Your Mileage May Vary. _Am |
Re: Premium gas...?
I'm a new HiHy owner and while I'm still in my break-in period, I noticed a larger than expected change when I used 91 vs 87 octane. Good explanation re compression and advance.
Anyone have sense (data) for % improvements for the various premiums available (e.g. 89, 91, 93, 94)? |
Re: Premium gas...?
Originally Posted by rudywalker101
(Post 132475)
I'm a new HiHy owner and while I'm still in my break-in period, I noticed a larger than expected change when I used 91 vs 87 octane. Good explanation re compression and advance.
Anyone have sense (data) for % improvements for the various premiums available (e.g. 89, 91, 93, 94)? Thanks. |
Re: Premium gas...?
Way too early for valid conclusions yet - as I'm only on my third tank. First was what ever dealer had originally, 2nd was BP 91 octane (BP is supposed to have good quality gas - low water/foreign matter), third is Sunoco 94. Will post info in database.
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Re: Premium gas...?
So based on what everyone has said, the HiHy gets better MPG with higher octane.
What's the general opinion on spending the extra $0.10 or $0.20 per gallon (for an average cost of $1.30 to $2.60 additional per tank) for the mid- or good-grade stuff vs using one of those off-the-shelf octane boosters (running $4 - $9 extra per tank)? |
Re: Premium gas...?
I have a 2006 Highlander Hybrid 2WD. I only got 20.3 mpg on a trip recently from San Diego to Tucson. I used 87 octane, temp was over 100, cruise control all the way at around 80. Tires all at 32. I took car into Desert Toyota and they said everything is normal and correct. Can anyone tell me what may be going on ? Service rep says there is nothing to adjust.
Thanks |
Re: Premium gas...?
Originally Posted by alex718
(Post 135289)
I have a 2006 Highlander Hybrid 2WD. I only got 20.3 mpg on a trip recently from San Diego to Tucson. I used 87 octane, temp was over 100, cruise control all the way at around 80. Tires all at 32. I took car into Desert Toyota and they said everything is normal and correct. Can anyone tell me what may be going on ? Service rep says there is nothing to adjust.
Thanks 80 MPH creates massive wind resistance that kills mileage. the hybrid offers no advantage when the engine is loaded heavily and continuously for long periods of time. The engine requires higher octane as the ambient temperature rises. At over 100 degrees, the spark advance is greatly retarded due to the 87 octane fuel resulting in lower mileage. The 100+ degrees has the variable speed electric air conditioner working at full power which reduces gas mileage. Your tires are inflated for a comfortable ride - not maximum fuel efficiency. Inflate the tires to the maximum pressure listed on the tire sidewall - 35 for the OEM Michelin and I believe about 40 for the OEM Goodyears. |
Re: Premium gas...?
Originally Posted by alex718
(Post 135289)
I have a 2006 Highlander Hybrid 2WD. I only got 20.3 mpg on a trip recently from San Diego to Tucson. I used 87 octane, temp was over 100, cruise control all the way at around 80. Tires all at 32. I took car into Desert Toyota and they said everything is normal and correct. Can anyone tell me what may be going on ? Service rep says there is nothing to adjust.
Thanks |
Re: Premium gas...?
Don R,
What a PERFECT response to Alex's post. It read like something Mr. Spock would have said on "Star Trek." On the other hand, Chilly summed it up pretty well in under 20 words. ;) |
Re: Premium gas...?
I have been tracking the mileage since March. Got the vehicle in February to replace my 1998 BMW 740i which was getting 23-25 mpg on the same trip from Tucson to San Diego. We go there every month to see my two kids. Usually I take my Ford F250 diesel since we alway bring way too much stuff with us. The huge truck gets around 19-20 mpg. So, like a dummy, I believed the quotes I heard from Toyota saying I would get 27 highway mpg and instead I get less than the BMW 8 cylinder tank. My normal in town mileage is around 25 mpg. Wife does most of the driving in town. I am going to inflate the tires to 40 and use a better octane fuel. The dealer says there is no engine adjustment however it seems the computer is programmed for power not economy. Are there any tuning variables that can be applied to the engine program ?
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Re: Premium gas...?
Originally Posted by alex718
(Post 135443)
I have been tracking the mileage since March. Got the vehicle in February to replace my 1998 BMW 740i which was getting 23-25 mpg on the same trip from Tucson to San Diego. We go there every month to see my two kids. Usually I take my Ford F250 diesel since we alway bring way too much stuff with us. The huge truck gets around 19-20 mpg. So, like a dummy, I believed the quotes I heard from Toyota saying I would get 27 highway mpg and instead I get less than the BMW 8 cylinder tank. My normal in town mileage is around 25 mpg. Wife does most of the driving in town. I am going to inflate the tires to 40 and use a better octane fuel. The dealer says there is no engine adjustment however it seems the computer is programmed for power not economy. Are there any tuning variables that can be applied to the engine program ?
1) Your BMW will get better mileage at 80 mph simply due to aerodynamics of the car vs an SUV. 2) Any diesel powered vehicle will outperform an equivalently powered hybrid or gas only engine at 80 mph. That is what makes the diesel engine so attractive. 3) the old EPA estimates were established back when the posted freeway speeds were 55 not 75 mph. the 27 mpg is based on on the old EPA estimates. If you are truly concerned about optimizing your fuel economy the BEST thing you can do is drive closer to 60 mph on the freeway I generally drive around 5 over the posted speed limit and If I recall correctly the posted speed limit for many of the interstates in AZ is 70 or 75 mph so it's not like you were speeding excessively. It's just the nature of the beast. I also would not recommend inflating the tires above the Toyota recommended PSI for the vehicle (this can be found on the door of the vehicle). I know it is a common practice here, but there are consequences, such as uneven tire wear and vehicle handling, that can result from running over-inflated tire pressures. |
Re: Premium gas...?
Chilly, thanks for your thoughts. I agree with your points 1-2. For 3, I am surprised that the EPA estimates are based on 55mph. Are the new ratings rules that are coming out changing the mph ?
Don R's point about octane rating and high ambient temperatures makes sense to me. I have always used the middle grade of gasoline in my BMWs and I guess I will have to do the same with the hybrid. I am not so overly concerned about the cost of the fuel, I can well afford it. I was just somewhat surprised at my resultant mileage. From a tire inflation standpoint, I have always religiously used the values that the manufacturer specifies since I have had performance oriented cars and their suspensions and handling design points are based on the inflation they publish. I keep my tires at 32psi cold which could be close to 40 psi when temp is over 100 and car is rolling at 80mph. So, I don't guess I will mess with that variable. BTW, I run my truck tires at 65-70 psi. The speed limit in Arizona is 75, crossing over into Calif it goes to 70. You might find me going more than 5 mph over in the boring stretches of desert on Interstate 8. |
Re: Premium gas...?
Originally Posted by alex718
(Post 135461)
Chilly, thanks for your thoughts. I agree with your points 1-2. For 3, I am surprised that the EPA estimates are based on 55mph. Are the new ratings rules that are coming out changing the mph ?
Don R's point about octane rating and high ambient temperatures makes sense to me. I have always used the middle grade of gasoline in my BMWs and I guess I will have to do the same with the hybrid. I am not so overly concerned about the cost of the fuel, I can well afford it. I was just somewhat surprised at my resultant mileage. From a tire inflation standpoint, I have always religiously used the values that the manufacturer specifies since I have had performance oriented cars and their suspensions and handling design points are based on the inflation they publish. I keep my tires at 32psi cold which could be close to 40 psi when temp is over 100 and car is rolling at 80mph. So, I don't guess I will mess with that variable. BTW, I run my truck tires at 65-70 psi. The speed limit in Arizona is 75, crossing over into Calif it goes to 70. You might find me going more than 5 mph over in the boring stretches of desert on Interstate 8. Here is a link the EPA test schedule. If you click on highway you will see they never go above 60 mph. The high speed, AC, and Cold Temp, test were just added recently and up until now, they were not include as part of the EPA estimate. http://www.fueleconomy.gov/feg/fe_test_schedules.shtml Also note that the average highway speed is only 48 mph. at 80 mph over a long stretch of highway, the EPA estimates don't even come close to representing your driving conditions. |
Re: Premium gas...?
I've been running 87 octane for a few weeks and the mileage has gone down. I'm going to run 91 of 93 this week and see if it makes much of a change.
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Re: Premium gas...?
I see the oil price peaked at 78.77 today for a new all time record. I wonder how long until the 4$/gallon would be a better calculation for the 87 octane vs. the 4.10$ for a 91 octane premium?
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Re: Premium gas...?
Originally Posted by w@ntonsoup
(Post 136798)
I've been running 87 octane for a few weeks and the mileage has gone down. I'm going to run 91 of 93 this week and see if it makes much of a change.
Net result, based on my one tank experiment? 33.26 MPG, a full 1.5 MPG more than the previous best tank that I had with the 87 octane, and 4.03 MPG over the average MPG of all previous tanks. Obviously I'll need to run some more tests to verify, but if I can average an additional 50 miles per tank, then that should justify the extra $1.70 (at most) it will cost to run with the mid-grade stuff. It will be interesting to see if 91 octane would give me an extra 100 miles per tank for the extra $3.40 (at most) it would cost. |
Re: Premium gas...?
Don R.
After about 2,000 mi, looks like 87 oct is giving me 28-29 mpg and 93 oct is giving me 30 - 31 mpg. From what I've read, a engine with a CR of 11 can use up to about 95 octane and still extract maximum efficiency (31 or 32% v. 30%). Have you tried 94 or 95 octane (mixing Sunoco 100 octane - race fuel available at some stations - with 93). It would be interesting to see what your Scan Gauge shows for timing advance at steady-state cruise. With Sunoco 100 selling at $6/gal, very doubtful this is cost effective, but might be possible to get 32 or 33 mpg. |
Re: Premium gas...?
Originally Posted by rudywalker101
(Post 138044)
Don R.
After about 2,000 mi, looks like 87 oct is giving me 28-29 mpg and 93 oct is giving me 30 - 31 mpg. From what I've read, a engine with a CR of 11 can use up to about 95 octane and still extract maximum efficiency (31 or 32% v. 30%). Have you tried 94 or 95 octane (mixing Sunoco 100 octane - race fuel available at some stations - with 93). It would be interesting to see what your Scan Gauge shows for timing advance at steady-state cruise. With Sunoco 100 selling at $6/gal, very doubtful this is cost effective, but might be possible to get 32 or 33 mpg. For another easy gas mileage boost, switch to 5W-20 oil from 5W-30 if you already aren't using it. It takes about a half hour of engine running to fully warm up the oil. The oil warms up slower than the coolant. Cold oil is a significant drag and the hybrid operation tends to keep the oil temperature low during city/suburban driving. |
Re: Premium gas...?
Will keep the tip in mind for next oil change, as we are in the 90's now in the Pgh area. Just performed my break-in oil and filter change and am trying Mobil 1.
For a list of Sunoco 260 GT100 Locations, check this site http://www.sunocoinc.com/Site/Consum...GT100Locations Doesn't look like anything in Chicagoland. (Note: This list is not entirely current, so call ahead). The location that I am going to try - Beaverun MotorSports Complex http://www.beaverun.com/ - is off PA Tpke exit 13 and fortunately is on my way to work (: |
Re: Premium gas...?
Using 0W-20 after my 5,000 mi oil change. Noticing significant effects of lower resistance. Under optimal conditions (30-40 mph P&G, some downhill). I'm seeing 37 - 41 mpg over a 40 mi leg. It's eerie now to see average digitial mpg rise as I'm driving up slight upgrade - where it had decreased slightly before.
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