Hi Brick,

You have been using Shell gasoline. Your trend values show 46.1 to 56.2 mpg indicated in somewhat adverse driving conditions which are better than anything I was getting with over 19,000 miles using Phillips 66. The highest mpg I ever indicated was 51.5 last Saturday using Shell gas.

What area of the country do you live in?

I know the Phillips 66 gas I have been buying is fresh and uncontaminated. My friends either own or oversee the fuel company that provides Phillips gas to this area and their quality is high. They maintain strict standards on their octane levels and actually keep only enough of the higher octane fuels in the ground to keep it fresh. They don't mix octanes. I've shared my observations of Shell gas with them and have told them I'm moving my other cars to Shell just to see what they'll do. They're interested to see what happens and I'll let them know one way or the other because they're my friends. They retail the mixtures that ConocoPhillips dictates.

Thanks for your feedback. Looks like Shell works for you too.

Ray

 

I'm in southern New England, and those tanks in the 46mpg range occurred with temps averaging 20F (colder in the mornings, warmer in the afternoons.) Now the average is more like 40F (mornings below, afternoons above.)

 

Another factor to consider is the percentage of ethanol in the gasoline, as this makes the FE ~3.5% worse with E10, for example. And don't assume that the gasoline/ethanol percentage for a given brand of gasoline is the same throughout the country. For example, Shell Canada informs me that in the major Canadian cities they are currently introducing a 10% gasoline/ethanol blend in their Regular ('Bronze' 87-octane) gasoline in order to meet the government's requirement of an average of 5% ethanol in their overall country-wide gasoline sales. Their 'V-Power' (91-octane) contains no ethanol, while their 'Silver' (89-octane) is a 50:50 mixture of the two, and so contains 5% ethanol. However, outside the major centers, none of their gasolines contains any ethanol. So, what you actually get, and so your FE, will depend upon where you fill up! I'd guess that the other companies may be following similar policies. How about in the USA?

Stan

 

That number is a bit too high. The energy content of gasoline is something like 35MJ/l whereas the energy content of ethanol is closer to 24MJ/l. So if you have 0.9l of gasoline plus 0.1l of ethanol (E10) you get (0.9l*35MJ/l + 0.1l*24MJ/l) = ~34MJ. The difference is (34MJ-35MJ)/35MJ = -0.03 or 3% less energy content per unit volume. That's approximately how much your volumetric fuel efficiency should decrease on E10 vs. straight gasoline.

 

I have to say that I get my fuel from a no-name dealer with a high turnover and I have had no issues in the past 10 years... it's when I go to a name brand station that problems start to occur. I think it has more to do with the station turn over rate. If the fuel sits in the tanks for longer periods of time, chances of more moisture entering into the system are greater. So I avoid all stations if possible with low turn over volume.

 

brick — You're quite right! I checked my references last night, and apologize for my faulty memory. I have corrected the numbers in my Post #13 above. Also wrong was the figure I gave for the percentage ethanol in Shell 'Bronze' gasoline — it's 10% not 5%. That makes their 'Silver' 5% ethanol. I have also corrected these numbers in Post #13. So, they meet the government's 5% ethanol overall requirement by selling 10%-ethanol gasoline in their highest-selling grade ('Bronze') in their largest markets.

Stan

 

I have learned that Shell 87 octane gas is improving my Prius mpg. Please read my earlier posts here.

Today is 4-2-2007. Over the past week my wife drove my 2006 Prius to Oklahoma (~600 mile round trip) and had to fuel with a different brand than Shell to return home. Mpg dropped 3-4 mpg on the gas she used (indicated at home was ~45 mpg and t-t was ~40.5 mpg). I refilled with Shell 87 octane and drove 340 miles to Kansas City again. When I refilled there mpg indicated was above 48, t-t was above 51. My 15 year old daughter drove back and constantly kicked the car into passing gear going up the hills and mountains and when we got home indicated was 47.4 mpg. I haven't refilled yet.

I plan on posting this on the data site as soon as I get the opportunity to put in order the thousands of miles of pre-Shell receipts I have.

If you are not using Shell gas, I encourage you to fill your next empty tank and try it for at least three full tanks.

Ray

 

Guys... brand names makes no difference, otherwise I should be getting low 40 all the time with my no brand name, instead i get high 40s low 50s. on a consistent basis with weather being the biggest factor.

 

livvie,

I'm glad you're happy with your mpg.

I filled my Prius tank this morning and drove round trip to a city about 80 miles away. My screen mpg reading was 55.0 when I pulled into my driveway higher than it's ever been and the main difference is Shell gasoline. I have to admit that today I drove between 65 and 67 mph because I'm happy about actually getting much higher fuel mileage and I wanted to see it actually go up.

You say fuel doesn't make any difference. I'm seeing at least a 10 mpg increase since switching to Shell 87 octane and I'll share this with others so that they can try it if they want. I've seen a continual increase as more of this fuel is burned. Eventually I'll see my mpg begin to flatline.

Phillips 66 is a top tier gas. So is Shell. My Prius likes Shell gasoline and I'm betting that other Priuses will too.

If you choose to keep your Prius for the life of the car, you're not doing yourself any favors by putting off-brand gasoline in it. You don't know what has or has not been added, and not all additives are good for your engine. Fuels without good (or any) additives will work in all cars for the short run but will cause engine damage over time.

I plan on keeping my Prius for at least 200K miles or until it becomes undrivable or too expensive to maintain. Engine upkeep and proper fuels are important to me.

Ray

 

Fuel economy is also strongly correlated to speed: you won't get very good mpg's at 75-80 mph!

If you want anything close to the EPA fuel economy ratings, you'll have to stick to the speed limit. If you want to go faster, then accept less mpg's.

Harry