My 1999 Saab 9-5 is supposed to get premium gas, which is about to throw me into bankruptcy. Does anyone know what happens if I start using mid-grade? Help, and thanks!
Under load, the engine will probably start pinging or knocking. The is a sign of early detonation. If it keeps up you can burn a hole in your pistons. The higher octane will help prevent the pinging or knocking.
Here is a link that might be useful: how stuff works
well lets think about this logically hmmm 7 year old depreciating asset and I have to spend extra dollars for premium fuel. I would do one of three things here No 1. Run it on regular gas till it pukes, its a depreciating asset junk it if it dies lol No 2. Sell this car and take my loss in one lump sum buy a nice fuel efficent grocery getter No 3. Keep buying premium gas and run the thing till the wheels fall off. I am not sure which way mathematically that the deal works best for you, probably all about the same ur just not in a good position with this vehicle. Personally if I were you I would only buy regular gas unless I started getting engine pinging under acceleration. Then step up to midgrade and see what I had if pinging is a problem. Most of the modern computer systems self regulate engine timing and the thing will probably run just fine just dont be street racing cuz the kid in the new Mustang might burn you bad.
Don't put any gas in until you are on empty so you will have the least amout of premium effecting the mid-grade. Fill it up and see what happens. If it start pinging and you feel uncomfortable put in a can of octane boost.
Check the octane requirements in your owner's manual. My BMW Z4 is supposed to get premium, but its octane requirements fall between mid-grade and premium. So I was told to alternate fill-ups of premium and midgrade, and to fill up at 1/4 tank. I have done so with nairy a ping to be heard.
I've experimented with changing octane ratings on a variety of cars; Taurus, Buick, VW and Audi. (BTW Audi manual asks for 93 octane). Pinging can be a problem, of course, but most cars these days have very good engine control systems. If you run too low an octane the computer will adjust timing and you will lose power.
The biggest effect I see is reduced MPG. If you go to the lower octanes you might get fewer miles per gallon, offsetting any cost savings.
No one ever mentions that what really counts is MILES PER DOLLAR.