My mileage went from 39 to 45? 2007 prius

[JacksonMs]

I have a 2007 prius touring... I drive about 100 miles highway round trip to work daily...
generally, my MPG is around 39 highway. The other day, I accidently filled up with premium unleaded instead of regular... My MPG increased to 45 with no change in the way I drive...
Has anyone else noticed a change in MPG based on what grade fuel they use?

Thanks!

[Sandy]

hi i get 45-50 on regular

[Omni-TaG]

I tried both premium and regular... i'm not shure but i think that stops and starts of gaz engine are smoother with premium grade.
Then i saw non diferences in gas mileage.

[Gadgetdad]

Originally Posted by JacksonMs

I have a 2007 prius touring... I drive about 100 miles highway round trip to work daily...
generally, my MPG is around 39 highway. The other day, I accidently filled up with premium unleaded instead of regular... My MPG increased to 45 with no change in the way I drive...
Has anyone else noticed a change in MPG based on what grade fuel they use?

Thanks!

This has been discussed before on PC. Most likely the difference is less air conditioning use now that fall has come. Short trips, cold weather, heater or A/C use, low tire pressure and aggressive driving accounts for low MPG's.

Premium gas in the Prius is just wasting $.

[Ophbalance]

Isn't premium supposed to be ethonal free? That might account for a gain of 3-10%, provided your regular gas has E10 in it.

[Gadgetdad]

Originally Posted by Ophbalance

Isn't premium supposed to be ethonal free? That might account for a gain of 3-10%, provided your regular gas has E10 in it.

Good point if the regular gas is watered down with Ethanol and the premium isn't. Out west here the same thing happens when the mandated winter gas is used with oxidizers (MBTE), you have to use more fuel to go the same distance. Handy for tax revenue for the State that requires it under environmental pretenses!

[uart]

Here in Australia we generally get a choice of three grades:

- "E10" containing 10% ethanol.
- "Regular" (sometimes just called unleaded, though they are of course all unleaded)
- "Premium" (various types of premium from the different brands, with various higher octane ratings).

E10 is the cheapest here, though typically only 1.5% to 2.5% cheaper than regular grade. Premium grades however are usually significantly more costly, typically around 10% to 14% more than regular.

I haven't made any systematic tests of Regular versus E10, though in tests that I've read they usually find slightly lower mileage with the E10, at least enough to nullify any benefit from it's cheaper price.

I did test one full tank of premium grade on the Prius just to see if it made any difference. The result was that the difference (if it existed at all) was very small, no more than about 2% (which could even have been natural variability). It certainly didn't justify it's 12% price premium.

[Frayadjacent]

Ethanol content is probably the culprit.

Higher octane gas is not about efficiency or power. It's about compression ignition (detonation) and avoiding it.

Using higher octane gas in a car that doesn't need it gets you nothing, all else being equal.

If you were stuck using E10 regular, and found some regular with no ethanol in it, you'd get better economy with the non ethanol regular.

[philobeddoe]

Originally Posted by Frayadjacent

Ethanol content is probably the culprit.

Higher octane gas is not about efficiency or power. It's about compression ignition (detonation) and avoiding it.

Using higher octane gas in a car that doesn't need it gets you nothing, all else being equal.

If you were stuck using E10 regular, and found some regular with no ethanol in it, you'd get better economy with the non ethanol regular.

nice avatar ... and i'm a fan of Ayn Rand as well


i've run the three available octane grades here in SoCal with no difference in mileage whatsoever

i'm not sure of the compression ratio of the Prius four banger, but i'm guessing it ain't 11:1

87 should do the trick

something else is accounting for your increased mileage

[bac]

Originally Posted by JacksonMs

I have a 2007 prius touring... I drive about 100 miles highway round trip to work daily...
generally, my MPG is around 39 highway. The other day, I accidently filled up with premium unleaded instead of regular... My MPG increased to 45 with no change in the way I drive...
Has anyone else noticed a change in MPG based on what grade fuel they use?

Thanks!

Holy cow! How do you manage 39mpg? Do you drive in the triple digits, or with the emergency brake on?

-Brad