grade of fuel

[attgig]

So, I'm doing a little research on cars that my mom would possibly buy. But as I'm doing some research (mostly on edmunds), it shows that some cars show premium fuel as a requirement (ie outback 3.0), while others show premium fule as recommended (ie volvo xc70).

what would happen if you didn't use premium on something that's required, and what would happen if you didn't use it on something that's recommended?

[Prngr44]

I'd check first to make sure it didn't void the warranty.

[DarkFury]

My thoughts (not necessarily the facts in this case) are that I generally use the recommended fuel (whether that be midgrade or premium... so be it.)

However... that being said, when gas prices shot through the roof, I did drop down and use the lower "required" fuel in my truck (dropping down to 87 octane). Since I have a "Superchip" in my truck, I can adjust the tuning a little bit to do this without a major sacrifice in performance. However, in my car, I still ran premium the whole time (it is also chipped), although the "required" was 89 octane. My chip was set to premium mode at the time.

I guess it just depends, however in light of your question I'd say... Use at least the "required" fuel for you car. If you want to squeeze a little more performance, then use a higher grade, but never go lower than the required unless you have a way to detune the engine to burn the lower grade fuel.

If you use lower grades than is required, you may suffer knocks and pings in your engine and your engine performance may suffer.

[guiseppewv]

My take:

Required = must use because the lower grade gas will cause a degradation in performance (e.g. fuel efficieny, HP, TQ, etc...) and premature detonation of the gas. This will slowly damage your engine if you continually use low octane gas.

Recommended = the computer will adjust the timing to use the lower octane gas, however, you will see a degradation in engine performance (e.g. fuel efficieny, HP, TQ, etc....).

[mechmike0034]

If I may, let me condense that a little...

Premium Fuel Required = must use because lower octane gas will damage your engine. Any resulting damage would not be covered by the manufacturer's warranty.

Premium Fuel Recommended = you will see a decrease in engine performance, but no engine damage will occur as a result.