arU4ic

2 of my Audis had valve replacements (blamed on 87 octane) until I learned my lesson, just use 91 and remove the doubt.

captain_video

None of the gas stations I frequent sell 91 octane, only 87, 89, and 93 octane fuel. I had a '99 B5 Passat 1.8T that I used to run 89 octane fuel and never saw any decrease in performance or gas mileage. I currently have a '14 A4 and a '14 Q7 and I run 93 octane in both of them. The local Shell dealers in my area run a special on Tuesdays where the price for '93 octane is the same as '89 octane so I just make sure to fill up on Tuesdays. Local grocery stores here also have a fuel rewards program whereby you get a discount on gas as you accumulate points when you shop. I let my wife use the rewards card when she fills up the Q7 since it gets worse mileage than my A4.

I would never run 87 octane in a car when the manufacturer recommends 91. 89 octane is a bit of a compromise, but with the discounts I can get it just doesn't pay to use the cheaper gas.

dreadlocks

here its 85, 87, 91.. even RUG vehicles run like crap on 85, gotta put "mid grade" in my Jeep or it runs worse than usual.. pay attention when you come to Colorado.

captain_video

I wonder if that's because of the higher elevation and lower oxygen content at that altitude. I would imagine that your Jeep just needs to be re-tuned to function properly at that elevation.

dreadlocks

its EFI so it should adjust fueling based on the air, but also because its got less air, its got poor cooling and your also beating on it harder to do the same as sea level.. so if it has to start pulling the timing (which its gonna do in these conditions with very low octane fuel) it really hurts.. FI vehicles up here still have the power, but EGT's and temps can get outta hand fast due to the lack of air because they are all working harder.

the only way you notice fuel octane power differences is if your ECU is retarding timing based on knock sensor monitoring (your pre-detonating your fuel), If you put higher octane than the tune needs you often wont see much if any gains.. if you put lower octane than it needs then it pulls the timing dramatically and it zaps quite a bit of power.

When I was tuning my big turbo race car w/methanol injection, the sweet spot for power on the dyno was adjusting the timing so it was being retarded just slightly, netted me +60whp over premium tune timing.. but if the methanol tank ran dry, it dropped by like -90-100whp as the tune would basically go limp and pull the timing harder than had I left it where it was originally... the ECU decides what your timing is but the further away from the expected tuning values it gets then the more safety multipliers start nerfing things.

bspurloc

here I think 93octane is $2.93 at costco, the only other offered is 87octane at $2.78
Buying 15 gallons of the 87 saves $2.25. why even bother.
I used to calculate how many gallons to buy of 87 and 93 to equal 91 then realized for what? to save $1.50?
My fill up says 91 - 95 octane. so by some of the logic expressed using 91 octane instead of 95 may be bad... of course which is silly.
Using lower octane wont hurt the engine. The PCM just adjusts the Timing. it is not being overworked or any of that that is just silly.
It does not do any work whether the gas is 95 octane or lower. It merely changes the ignition timings which is the same work it does regardless of anything. it doesnt need to do anything different. it doesnt cause valves to go bad or anything. the engine isnt doing anything different. the explosions from the gas igniting just have less force. they are not Dirtier. the only thing affected is your 0-60 times. your passing times, your top speed times. beyond that once the car is moving the car is moving.
You are not going to get any different mpg on the hiway at crusing speeds and if you think that then please explain to me how corvettes and other engines over the years can turn off 4 cylinders to increase MPG when that obviously cuts the HP in half. which is a more significant hit than lower octane gas.

landragon

Your car will work fine without premium gas but the cars computer can sense engine knock through the knock sensor and it will delay your ignition timing.

Basically if your igniting timing event occurred at 20deg before top dead center, it will delay the timing at maybe 10deg to reduce the engine knock. And why is delaying the timing bad? Because it is reducing the pressure inside the combustion chamber and that also means the air/fuel mixture is also under less pressure so when it gets ignites by the spark plug it doesn't expand as strongly resulting in less power out of your engine and less gas mileage.

TLDR; non premium gas = less power out of your engine = worse gas mileage.

So in the end you're not saving anything and you're just wearing out your engine for no reason. Can you use non premium if you're in a bind sure.. but other than that you're just screwing yourself

not2fast

I go all in on Whiskey (KOVAL) and Vodka (KETEL1). Buying what I like regardless of price. (Costco and Total Wine have great prices here)

Fuel it really depends on the application. Honda Pilot gets 87, VW Passat 3.6L gets 89 or 92 octane, Q7 gets 92/93, boat gets 87, and my waverunner gets 93 octane. Waverunner, boat, lawn mower, leaf blower, and snow blower get non-oxy fuel at end of the season.

Most of the gas stations around me don't offer true premium. They have prpremium non-oxy which is 91 octane. It is about 70 cents a gallon more than 87 octane. I had to shop around to find gas that offered something else that either offers 92 or octane usually 20 cents a gallon cheaper. The non-oxy is great for my waverunner, boat, mower, and snow blower though because of its longer shelf life. When I used to race an open wheel formula car I used to buy barrels of VP racing fuel and tune to that fuel. It was easier than tracking down fuel and hoping it works with my tune.