do you have to use premium fuel if your car says that’s what it takes?

If your owner’s manual calls for premium than YES you need to use premium. Using a lesser grade can damage your oxygen sensors and other components of the emissions system.

Don’t bother with 91 octane. Not much performance from that car anyway. Just save ur money and get the cheapest fuel u can find.

It’s no lie. Meet or exceed the octane requirement.

Yes you need to follow the instructions, if you use a lower grade it can make your engine start knocking. Also you could put lower grade in but you will need to buy octane booster from either auto parts store or i think wal mart carries it too.

I recommend reading the US Federal Trade Commission’s Facts for Consumers – “The Low-Down on High Octane Gasoline”
http://www.ftc.gov/bcp/edu/pubs/consumer/autos/aut12.shtm

You should use whatever grade/octane the owner’s manual recommends.

If your car is experiencing engine knock (or pinging), then you should go up a grade in octane. (But if your car IS knocking, something may be wrong with it and it may need a tune-up!)

Octane is a measure of the fuel’s ability to resist pre-detonation (or engine knock).

Higher octane gasoline doesn’t mean that it is necessarily cleaner or better. “Premium” is a mis-nomer. All gasoline sold in the US must meet certain federal EPA clean-burning guidelines. However, some individual brands _may_ decide to put some extra cleaners or extra refining in their higher-octane fuel (as I’ve heard of some brands advertising low-sulfur gasoline as only in their Premium line).

A higher octane gasoline actually has lower BTUs (energy content) than a lower octane gasoline, so the only way that you’d see better fuel economy by going up in octane is if you were previously using lower than recommended octane in your car…

For an occasional tank, you could get away with using a lower octane than recommended in a car that requires “premium” fuel, like yours, as the car will adjust, but it can cause some extra wear on the engine while knocking, besides the lowered fuel economy. (long term use can cause additional engine wear/damage)

If you live in a high altitude area (like the Rocky Mountains) usually you can use the next octane level down from what is listed in the owner’s manual because of the altitude/thin air with no ill effects (except if you come down from the altitude with a full tank!).

For some cars, such as the Toyota Prius, using higher than the recommended octane fuel is known to cause check engine lights with engine misfire codes (because of the Atkinson cycle engine, rather than the Otto cycle engine most other cars use) due to the late detonation, besides the expected lower fuel economy.

Reasons to use higher octane fuel:
1. Your owners manual calls for it
2. Your engine is knocking
3. It’s the only way to get low-sulfur fuel in your area (sulfur will slowly poison your catalyst, making emissions worse over time)
4. You like spending extra money on gasoline

In much of the US, 91 octane ((R+M)/2 method) is the mid-grade gasoline, so it’s not that that much more expensive.

See also:
Premium vs. Regular : http://cartalk.com/content/features/premium/

Yes, you should because,if the car recommends is that means the engine is easily damaged by gasoline residue.The difference between gasoline types are how clean they burn, the lower the octane the more residue it leaves behind.