running on regular unleaded (v6 3.0)

[road_tripper]

I just finished a road trip of over 2600 miles. I decided to see the difference between running regular (87 in these parts) vs the 91 'recommended'.

My trip went from Las Vegas -> Bellingham WA -> Sunnyvale CA -> Sequoia NP -> Las Vegas

Probably 90% highway 10% city, driving the speed limit or with traffic, whichever was faster :) When in Rome...

Overall I got 24.9 mpg. High was 27.5 mpg driving from Ely, NV to Caldwell, ID (408 miles), on 85 octane fuel (high altitude).

No weird problems, but a definite loss of 'performance' (acceleration butt dyno confirmed).

I did this because I am cheap, and when driving on these road trips, the price difference between 87and 91 octane is usually 45-50 cents, highest I've seen is 60. When fuel was $2 a gallon, a 25% increase from regular to premium always struck me as a bit offensive. The worst place is Pilot when their non-diesel fuel is supplied by Shell. (One place I refueled: https://www.gasbuddy.com/station/188666 3.29 for regular, 3.85 for premium) Other places only charge 22 cents more for premium.

At any rate, the car ran well. I have 270,000 miles on it so still getting pretty much original EPA fuel economy. Nice to know if I am feeling especially penurious I can choose the 'regular' fuel for a discount and not have to worry about pinging, increased fuel consumption, or dirty looks from the 'you are running regular from a non-TopTier fuel supplier' crowd. I usually do only get toptier fuel, but on this trip I decided to slum it on a few tanks!

[AudiA4B61.8T]

So the real question is did your fuel economy suffer going from premium to regular or only a loss in spirited riding performance?

[MSq5]

I just finished a road trip of over 2600 miles. I decided to see the difference between running regular (87 in these parts) vs the 91 'recommended'.

My trip went from Las Vegas -> Bellingham WA -> Sunnyvale CA -> Sequoia NP -> Las Vegas

Probably 90% highway 10% city, driving the speed limit or with traffic, whichever was faster :) When in Rome...

Overall I got 24.9 mpg. High was 27.5 mpg driving from Ely, NV to Caldwell, ID (408 miles), on 85 octane fuel (high altitude).

No weird problems, but a definite loss of 'performance' (acceleration butt dyno confirmed).

I did this because I am cheap, and when driving on these road trips, the price difference between 87and 91 octane is usually 45-50 cents, highest I've seen is 60. When fuel was $2 a gallon, a 25% increase from regular to premium always struck me as a bit offensive. The worst place is Pilot when their non-diesel fuel is supplied by Shell. (One place I refueled: https://www.gasbuddy.com/station/188666 3.29 for regular, 3.85 for premium) Other places only charge 22 cents more for premium.

At any rate, the car ran well. I have 270,000 miles on it so still getting pretty much original EPA fuel economy. Nice to know if I am feeling especially penurious I can choose the 'regular' fuel for a discount and not have to worry about pinging, increased fuel consumption, or dirty looks from the 'you are running regular from a non-TopTier fuel supplier' crowd. I usually do only get toptier fuel, but on this trip I decided to slum it on a few tanks!

I would be more concerned about your ECU pulling timing like crazy to prevent detonation and the effect on fuel trims. Lower octane actually burns hotter, too, increasing exhaust gas temps. Might not be so good on your cats.

Interesting experiment, but not sure it is safe except for very short term.

[road_tripper]

So the real question is did your fuel economy suffer going from premium to regular or only a loss in spirited riding performance?

I think for highway driving at 80mph, the fuel consumption is the same. I can remember back when my 3.0 had less than 100K on it, I was driving north on I-15, filled the tank in spanish fork, ut and made it 460 miles on fumes to rocker, mt. Probably put in 17 gallons, so about 27 mpg. I did slow down to 60mph or so for the last 30 miiles or so as my 'distance to empty' was at zero.

So I think no reduction in fuel consumption. On these drives, though, I only shift gears a few times, just to get from gas station on to the interstate, then I leave it in 6th for hours and hours and hours, until the fuel runs out. I never have to downshift for any hills/passes, running on the regular or premium.