Way back when, I had a SWEET 1979 Dodge Omni 024. Every time I shut the engine off, it would run on. When I switched to Premium fuel, the run-on went away. So, I figured the premium must be doing something good for my car, and have only used it ever since (Except when I had a Diesel Rabbit, but that is another question!)
I figure it is a couple more bucks per tank, but worth the peace of mind for me. Anyone else use Premium when they don't have to, or am I just trying to relive fond memories of the 024?
2007-07-23 16:41:18 · 6 answers · asked by Cheesetoasto 3 in Cars & Transportation ➔ Other - Cars & Transportation
The answer about carbon build-up is probably right. In that case the high octane fuel resists igniting without a spark ('Dieseling'), which is what causes 'running on.' Higher quality fuel (not neccessarily higher octane) can help prevent carbon build-up.
The question about octane keeps coming up and there is always someone with disinformation posting an answer. The dude who says high octane runs hotter has it exactly backwards.
Octane rating is a measure of resistance to preignition (knock). That means that the higher octane fuel takes more heat and pressure before igniting without a spark (You definitely DON'T want the fuel/air mixture igniting when the piston is still moving UP in the cylinder!). Higher compression engines need it because Boyle's Law says the higher pressure means higher temperature, which increases the danger of preignition.
Most modern cars have a knock sensor that listens to the engine and retards the spark if 'incipient knock' is detected, in case you find yourself in a situation where 91 octane is not available.
Retarding the spark means that the spark occurs earlier in the combustion cycle. It does nothing to lower compression, but because the spark happens earlier, it short-circuits the preignition cycle.
This will reduce the engine's power, though.
The only damage high octane fuel does, if your engine doesn't need it, is to your bank balance.
There is NO benefit to putting high octane gas (as opposed to high quality gas) in an engine that only needs regular. It's like expecting a guy who spends all his time on his butt watching TV and playing computer games, to run a faster 1/4 mile after drinking Poweraide. Dehydration and electrolyte imbalance are not the reasons he's slow. It can't solve a problem he doesn't have.
Thanks to allanatherton for correcting my misinformation on retarding the spark.
2007-07-23 19:17:15 · answer #1 · answered by theomdude 5 · 0⤊ 0⤋
I have a Dodge Durango and in the manual it says: Absolutely do not use premium fuel! Using higher octane than recommended can do harm instead of good. Premium burns hotter which would be hotter than what your engine is designed for. Only use the recommended octane rating listed in your vehicles owners manual. Using any other can actually decrease the life of your engine. My S-10 (1991) has 215,000 miles and still running strong using regular unleaded. In its lifetime I have had an engine induction done 3 times to get rid of carbon buildup. The truck doesn't smoke, doesn't burn oil and has awesome fuel economy to this day. If you follow the recommended oil change and maintenance intervals, etc. it'll give back to you what you put into it. As for your dieseling problem, I'm sure it was caused by something other than the gas you were putting into it.
2007-07-24 00:00:26 · answer #2 · answered by wasntme012002 3 · 0⤊ 1⤋
It sounds like your 024 was dieseling on you. That could have been some other problem like carbon build up or the timing may have been too far advanced.
If my car calls for regular, then that is what I put in it. The cars are computer controlled now, so that should help.
2007-07-23 23:46:50 · answer #3 · answered by Fordman 7 · 1⤊ 0⤋
It is cheaper to do a tune-up, or to shut the car off in gear than to waste premium fuel and the money to pay for it, unless the manual calls for premium.
2007-07-23 23:54:10 · answer #4 · answered by Fred C 7 · 0⤊ 0⤋
about every 5 or 6 tanks full i use high test ,i think it helps keep the engine cleaned out good,but i don't use it all the time,most of the time i run regular,but the run on you speak of is very aggravating sometimes,some cars like high test,and some will run on anything,i usually go by what the owners manual says to use,good luck with it.
2007-07-23 23:51:17 · answer #5 · answered by dodge man 7 · 0⤊ 0⤋
my car TAKES premium..so I always use it, but my sister who drives a Honda, uses mid-grade, instead of low octane...I always think Hondas like higher grade fuel than what the manual says...and I also think all gas is NOT the same...
(Honda/Acura driver for 26 yrs.) My cars have NEVER liked Shell,Exxon, Amaco,Mobile or 'cheap no name' gas...
2007-07-23 23:57:02 · answer #6 · answered by Chrys 7 · 0⤊ 0⤋