Regular vs Premium Unleaded?

[COACH_EM_UP]

I run 87 octane in the 2000 Civic. Tried the premium but got worse mileage with the premium than the 87. The truck also gets 87 octane.

The Camaro gets premium and the wife's car is supposed to, but she puts the cheap stuff in there. I put premium in the boat and ethanol free before putting it up for the winter months.

[powderburner]

I had a Hyundai Equus. Bought of the Hyundai show room floor when it was Hyundai. That is the only vehicle that I have ever had that I could tell within a few miles when it did not have premium in it. V8 ran like a scaled ape. But would blow smoke and run like crap on anything but premium.

man I wish I never sold that one.

[imyomama]

I had a TRX Launch edition truck with a 700 horse power engine with a super charger.
Regular gas was 4 miles per gallon less than regular.

not sure how that works ???

[Walker]

The engineers that design these engines are way smarter than most of us. Run what is recommended and you'll be fine.

[adam_p]

Y'all can put 87 in your high compression motors and rely on the knock sensors to keep from burning a hole in a piston but I'll just keep paying the extra money for the correct fuel.

[imyomama]

i know on the ecoboost ford you have to run premium for a while for the computer to learn and adjust the fuel mapping accordingly... mixing 15 gallons of premium with 11 of regular may equate to mid grade overall ..

my new truck has 36 gallon tank ... i can't afford to fill it up with premium without getting a bank loan...

[Bucknaked]

So 2mpg lesser gas mileage is all you have noticed with no power loss? If that's the case, I can't imagine the extra cost being worth it until costs go down.

These Gubment motors 6.2’s require premium so that’s what I use! Higher octane and that’s manufacturers specs- specified for a reason !

[jdg13]

A high performance high compression engine benefits from premium, but not many folks grocery getters fall in that category. The only real "premium" gas is the ethanol free stuff anyway. You may see a slight mpg boost since there's no corn in it, but for a daily driver the per gallon cost would still outweigh the mpg savings.

[muzzlebrake]

Premium fuel is higher octane which burns slower and allows the engine to run more advanced timing, usually around +5 deg, which equals more HP which equals better efficiency thus better fuel mileage when operating normally. You keep your foot in it all the time there won't be a difference in economy.
Now you may not feel a 5 deg timing retard but your time slip will show it

There are tuning methods that can be used, requires a dyno, that can make any of these fuels work better than factory maps and raise the engine's output 10-15% but that's another subject. All factory engine tunes leave horsepower on the table for longevity and warranty reasons and EPA CART regs.

When I was dyno tuning Harleys I used TTS Mastertune and could take a stock Harley TC 103 injected and pull another 10hp and 10tq from most engines with no other mods using 87 oct and boost the mileage from 35-40 mpg to as high as 52 mpg highway running speed limit which nobody does

[muzzlebrake]

These Gubment motors 6.2’s require premium so that’s what I use! Higher octane and that’s manufacturers specs- specified for a reason !

True. My impression is that it's related to the DFM and VVT mechanisms where pre-ignition aka ping aka detonation is hard on all valve train components. They have enough trouble with this crap already. Therefore the engines survive better with slower cooler burning fuel.

[CaptainDave]

If the vehicle manufacturer recommends premium, I'll run premium. It never even crossed my mind to run premium in a vehicle that the manufacturer didn't recommend to do so. The cost difference is most definitely noticable.

Other than higher performance sports cars, I've found that a lot of vehicles that are recommended to run on premium have turbos. You know, the 4 or 6 cylinder turbo engines. Lots of foreign premium sedans and SUVs are designed this way. Heck, even Jeep pushes a 4 cylinder turbo in their wrangler line, for which premium is recommended. I'm sure Ford recommends premium with their ecoboast engines.

What does this mean to me? For starters, when looking at gas mileage on a vehicle, the requirement to use premium over regular should also be assessed. My wife's last vehicle was an Audi Q5. We replaced it with a Lexus RX 350. Other than added reliability of the Lexus brand, it was nice to find out that it came with a normally aspirated 6 cylinder engine with the recommendation of regular gas. Sure, not as fun or sporty, but paying almost a dollar less per gallon for regular is nice right now.

[Landrover]

I run regular in my Tundra, but my wife G-Wagon will only see Premium no matter what it costs.

[jaime1982]

Clearly so many have theories but have never run full spec analysis on fuels.

OP, to answer your question. The only advantage is octane or AKI. The boiling table is slightly different between 87-93 but not much, not every high octane component is heavier.

Gas is a mixture of many different components with different boiling points ie (butane, LSR, reformate, fcc cat gas, alkalyate, SCN ect).

Here is how we test for octane

[Bucknaked]

Clearly so many have theories but have never run full spec analysis on fuels.

Here is My analysis- when gas gets more expensive they will shut down their unleaded pumps and the only thing we’ll be able to get is Premium anyway- it happens after every hurricane and happened in 08 and many times before that ! My truck will continue to drink premium.

[Chase4556]

i know on the ecoboost ford you have to run premium for a while for the computer to learn and adjust the fuel mapping accordingly... mixing 15 gallons of premium with 11 of regular may equate to mid grade overall ..

my new truck has 36 gallon tank ... i can't afford to fill it up with premium without getting a bank loan...

I’ve got the 3.5 eco and the 36 gallon tank. Wife picked me up from the airport the other day with 1/8 tank. $124 to fill it up. Gah. I’ve never run premium in it… maybe I should do a couple tanks and compare my gas mileage.