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Regular gas in Premium Engine

I’m looking to buy an old Aurora 2003 with the V8 engine, Oldsmobile says that this engine gotta run on premium fuel, the car have over 200k km and Im pretty sure people put regular fuel in it.

I know the motor could loose power and gas millage doing that, but if I buy the car and start putting Premium in it, will the HP and millage will be back or it will still work like on regular fuel?, Thanks!

If the engine requires premium and was run on regular, walk away, there are plenty of other cars to look at. If premium is recommended it is worth taking a look at the car. Your mileage probably won’t change much. Spend $100/$150 to have a mechanic look the car over before you buy it.

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Any time you are looking at used vehicles and there is even one question about it in your mind look elsewhere.

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Fuel economy can vary considerably. A test V6 Aurora averaged 21 mpg, and a V8 just 14.1 mpg. Oldsmobile has recommended 89-octane fuel for both engines.

I might be alright ahah!

Here is a good article by Edmunds on that.

Just read the owner’s manual;
If you have the 3.5L V6 engine (VIN Code H), use
regular unleaded gasoline rated at 87 octane or higher.
If you have the 4.0L V8 engine (VIN Code C), use
premium unleaded gasoline rated at 91 octane or higher
for best performance. You may use middle grade or
regular unleaded gasolines, but your vehicle’s
acceleration may be slightly reduced.

Thanks y’all!

I don’t believe that car was available with a V-6 in 2003. The owners manual that I am reading states that 87 octane is acceptable;

Use regular unleaded gasoline with a posted octane of
87 or higher. However, for best performance and for
trailer towing, you may wish to use middle grade
or premium unleaded gasoline. If the octane is less than
87, you may get a heavy knocking noise when you
drive. If this occurs, use a gasoline rated at 87 octane
or higher as soon as possible. Otherwise, you might
damage your engine.

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If the vehicle REQUIRES premium then use premium. You can destroy an engine if the knock sensor stops working.

13 year old vehicle from a discontinued brand with 200,000 KM and may have had wrong fuel all this time. Why would someone even look at it ? I wouldn’t.

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I came here to ask that question. Regardless of gas, why buy this car? Take that money and buy something more reliable/economical/repairable. The V8s in these cars were troublesome (like the related Northstars in the Caddys).

It’s cheap and that’s all the buyer is able to pay?

Back in the '60’s my brother and his buddies in the Navy at Norfolk would pitch in and buy a $50-100 car to drive to DC on leave.
Most times it would make it round trip; sometimes not.

I am sure this car came with a knock sensor. This is to prevent detonation to save the engine in the event lower grade fuel is used. The engine computer backs off the timing which also reduces power and economy. Yes, it can be run but it is best to run what the engine is designed for. If you get this car, I suggest getting a big discount, otherwise just walk away.

If the engine checks out good, than it hasn’t suffered any permanent damage. If you put it back on its proper fuel it should get the best performance and mileage a 2003 Aurora V8 can get based on the rest of its history. If you do buy it, regardless of what it’s been run on in the past I recommend using premium. You COULD still cause damage in the future.

Get it checked out by a good mechanic. If you like it and it’s in good shape, go for it. If there’s any question, keep looking.

If premium is only suggested, but not required, and regular is ok to use according to the owner’s manual, then using regular will be ok. The engine computer will soon realize regular is being used b/c the engine will start to ping, and the engine computer will respond to that by retarding the ignition timing and perhaps other things, which will end the pinging. The downside is the acceleration might be a little slower than before. If you want to worry about something, worry about the ping sensor. It is critical that is working correctly for this all to work. When pinging occurs, it can damage the engine. In a big way, like burning a hole through the piston. Yeah, like you got a welder inside your engine, it gets that hot and bothered when it pings. I expect though you’d be fine to use regular, and no damage was done to the engine using regular in the past. Bad pinging is usually very obvious to the driver, it sounds like someone is rattling a coffee can full of nuts and bolts.