does anyone know if using premium gas in a old car can cause it to not start:confused:
It should run fine if it requires unleaded.
Try asking the question in your title for more answers in the future. You’re in the wrong forum too. I tagged this thread for a moderator can get you in the right place.
Moved from ATMB to General Questions, and edited title.
Colibri
General Questions Moderator
thank you so it would not be the fact that i put in some premium, it wont start
Something else happened and using premium is just coincidental.
thanks so much for the help
Assuming the gas it good there should be no problem from that.
Using premium gas in an old Beetle on a hot day may make the car is a bit more likely to overheat. I’m not sure why. I’m guessing the different combustion rate causes the engine to effectively run a bit lean. Once it overheats, it may not start again until it cools down.
Other than something like that, I can’t think of any reason why premium gas would cause a car not to start. The car may not run as well on premium as it would on the octane it is designed for (yes, you are probably paying more to make your car run worse), but it should still run. If the car has a lot of carbon buildup in it, using premium may actually make it run a bit better, since the carbon buildup will cause a higher compression and may make lower octane fuel spontaneously combust before the spark is supposed to set it off. Most of the time though, if the car isn’t designed for high octane fuel, you are just wasting money. The car may run slightly worse, but not enough that you’d ever notice.
What exactly are the symptoms? Is the engine cranking, or is it just going click click click? Is it starting to catch at all or does it just crank?
Another vote for coincidence.
A sort of aside Q
Would premium gas be worse for cold weather starting?
Reasoning: Premium gas has higher resistance to detonation, perhaps harder to ignite.
How old? Make and model?
maybe a little, but the big difference would be using summer/warm weather blends during the winter. the overall fuel blends are adjusted throughout the year to account for seasonal temperature changes.
IANAM - but higher octane (8-cabon chain) means lower (7-carbon chain) heptane (usually) meaning the gas does not explode as easily. It need higher compression or it burns slower. The advantage is that in a high compression engine (like many fancy/performance cars) you are less likely to get knock (premature spontaneous ignition) of the gas as the piston compresses it. If you run it in a regular engine, it burns later and faster(?) giving a hotter-running engine.
In an older car, where the compression may be bad since the cylinder is worn, leaks a little, and so compression is worse (lower), it is likely that the combustion will be slower, less complete, and you will get worse performance than regular gas. In an older car where the engine is still in good shape, and compression is still good - the engine will run hotter, which may help burn off accumulated carbon from incomplete combustion.
Of course, the carbon buildup and incomplete combustion, IIRC, were a feature of pre-1980’s carburetor engines. Computerized fuel injection engines in recent history have made a point of regulating the amount of fuel injected, so that there is a lot less incomplete combustion and carbon buildup is much less.
This is what I’ve gathered over the years, but maybe a real motor expert can clarify…
The difference between winter and summer fuel is in the vaporization pressure. Summer fuel has a higher vaporization pressure so that the fuel doesn’t easily evaporate into the atmosphere under higher ambient temperatures. It’s unrelated to the fuel’s octane rating. Nor do I see any reason why octane rating would affect cold weather starting - it’s a measure of the fuels propensity to auto-ignite, putting a spark to it is going to set it off regardless.
I think the variation in fuel vaporization rates did cause problems with carburetors, and contributed to the difficulty of starting a carbed car in cold temps, but it’s not really an issue on a fuel injected engine.