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)?

Could you give some more information about your experience? (number of tanks, fuel economy and grade of gas used on those tanks, etc.)

Thanks.

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.

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)?

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

What gas mileage do you get for your normal driving routine?

80 miles per hour 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.

You got 20 mpg out of a V6 270 hp SUV at 80 miles per hour. I don't see the complaint?

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.

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 ?

I have never had a car meet EPA est. That's just me. That being said I have 3 quick points.

1) Your BMW will get better mileage at 80 miles per hour 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 miles per hour. 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 miles per hour. 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 miles per hour 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 miles per hour 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.