1997 850 Premium Fuel

[davolvo]

I made a 60 mile trip this morning and the gas gauge hardly moved. For kicks and giggles I topped it off and it only took 2.1 gallons. I was traveling 55-65 mph. Could premium and Lucas make that much of a difference? Or as someone mentioned is my O2 sensor going out?

[warcraftjunkie]

Here in Salt Lake City and other "high elevation" locations regular unleaded is 85 octane and the premium is 91 (almost always with ethanol in it). There is one station in town that sells true 92 octane with no ethanol but unfortunately it's 3.89 a gallon.

Is the lower octane rating because of the higher altitude here contains less oxygen already thereby allowing fuel manufactures to sell gas with lower overall oxygen content?

[jblackburn]

Is the lower octane rating because of the higher altitude here contains less oxygen already thereby allowing fuel manufactures to sell gas with lower overall oxygen content?

http://www.denverpost.com/latin/ci_4503169

[burnout8488]

I ran 87 in my 99 when it had the 13T on. (Basically a GLT)

It made absolutely no difference. I saved money. It ran perfect. The manual also says 87 is fine. Yes, even on the low pressure turbo.

Now that I'm tuned with a 15G it sees nothing but premium (93 octane) because I value my pistons, but prior to that I saw absolutely no difference.

Hope this is a useful data point.

[QuirkySwede]

Could premium and Lucas make that much of a difference?

Premium, yes.

Lucas, no.

How one drives makes the biggest difference. Temperature and altitude do too as higher, warmer air offers less resistance and better economy. Head wind, tail wind are also big factors which why speed records must be run in both directions and then averaged.

[instarx]

Premium, yes.
Lucas, no.
How one drives makes the biggest difference. Temperature and altitude do too as higher, warmer air offers less resistance and better economy. Head wind, tail wind are also big factors which why speed records must be run in both directions and then averaged.

I agree. One trip isn't enough to prove any difference. Psychology, for example, plays a huge part. Because you are expecting/hoping for better mileage you may drive a tiny bit more conservatively. You won't notice it, but your MPGs will. That's why experiments are done blind - in this case the driver should not know if the tank holds premium or regular. Since that is impossible in the real world you have to make many trips to get a true reading, which also averages out environmental factors. Keep testing.