Fuel Economy Discuss tips and tricks for better fuel ecomony.

Using regular fuel instead of premium fuel?

Old 08-02-2013, 05:32 AM
Junior Member
Join Date: Jan 2012
Posts: 10

Thats was a nice link you shared. There are undoubtedly some advantage for premium fuel as compared to regular ones. theres some reason why it would cost more..
Old 08-04-2013, 05:50 PM
Join Date: Apr 2013
Location: Singapore
Posts: 27

Agree with kanarrjl, try out the regular and premium fuel for your car for a couple of tank each. Feel your driving experience and calculate your mpg, some cars may get a better mpg and driving experience using premium, measure against the price difference, you may get better fuel/cost efficiency.
Old 09-02-2013, 08:24 PM
zerojett's Avatar
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Join Date: Dec 2007
Location: Saskatchewan, Canada
Posts: 686

Originally Posted by kanarrjl View Post
It won't hurt to purchase a higher than recommended grade either so I recommend trying the minimum that your car can handle for say 3 tanks and see what your mpg's average out to. Then try premium for 3 tanks straight and see what your mpg's average out to. I had an old dodge ram that got me a constant 8mpg on regular and 11mpg on premium, it was enough to warrant purchasing premium.
there's a big difference when we're talking about an old vehicle that maybe haven't been as well maintained as it should have been, or has higher km on it. my dad had an old cutlass that would only really run on premium. this is apparently common on high mileage v6/v8's.

on a newer vehicle, where ignition timing is controlled by the ECU, and where the engine will retard the ignition timing when it senses knock, thus spitting more fuel to compensate for the delayed spark, you'll notice the disadvantages of running the wrong octane fuel pretty quickly... Excessive fuel/running rich is a big problem.

There was a whole documentary on Discovery about this, saying how a car that only requires regular, would burn excessively rich with premium. this can cause a whole slew of issues. washing out the cylinders so that no oil lubes the walls, causing excessive wear on piston rings, leading to plenty of blowby and increased crank-case pressure, which will eventually just start blowing out your cam seals and front/rear main seals on the crank. do you want that? probably not, unless you like spending money on repairs.
Old 01-03-2014, 07:01 AM
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Posts: 30

Originally Posted by trustdestruction View Post
The truth of these myths only apply to cars that are designed to run on regular-grade gasoline (87 octane). If the auto manufacturer says use 91+, use 91+. If it says to use 87, then use 87. The real truth of the myth about premium vs. regular is that the car will not likely see positive results by going higher than the manufacturer-recommended/required octane of fuel. Going lower than that though will definitely achieve negative results (reduced engine performance and/or gas mileage, and potentially engine damage due to misfiring/pre-ignition).

The reason that certain cars require higher grade fuel is usually (if not always) due to their higher engine compression, or put simply: higher pressure in the combustion chamber. This all has to do with cylinder/piston size, stroke, etc. The higher the pressure, or compression, the more likely it is that the fuel in the chamber will "spontaneously" detonate due to this pressure rather than waiting for the spark plugs to ignite it in a controlled sequence/timing. Without the right fuel, the end result is pre-detonation/misfiring.

This is where higher octane fuels come into play. Octane is a measure of a fuel's resistance to burn. The high octane fuel is more resistant to burn, and thus more resistant to the high engine compression, and when a high enough octane is used the fuel will not pre-detonate/cause misfiring. This allows the spark plugs to do their job and ignite the fuel in a controlled manner, resulting in a properly running engine.
WOW - that's a lot of info there. I always thought higher octane was more refined and burned hotter and thus cleaner. Thank you for explaining octane ratings, that was a real eye opener
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