Hello all,

I know this topic has been beat to death, but...
Called the dealer today, he asked what grade fuel I was running, I replied "premium 93 octane".
He then proceeded to explain the higher the octane the slower the burn (which I knew) which in turn leaves larger carbon deposits on the top end.
Dealer suggested numerous times 89 octane!
Said many of thier cutomers run it and have never had problems.
What gives? The price to me doesn't make a difference, Iam concerned about predetonation (pinging).
The dealer even went so far as to say my fuel consumption may go down.

Sure someone has thoughts on this

Regards,

Nick

 

Detonation margins are moderate in these engines and there are knock sensors on the block to retard the ignition timing if knocking is detected. That said, most people report WORSE fuel mileage on lower octane fuel because as the knocking increases with power output, the ignition timing is progressively retarded to compensate, even if you can't hear it, affecting power output and combustion efficiency. If anything, the carbon problem will get worse as a result of lower octane fuel.

In my studied opinion (I have done quite a bit of research on the effects of octane and mixture management in aircraft piston engines), your dealer is giving you bad advice. He is also claiming more knowledge of the detonation margins and fuel needs of the engine than the engineers who designed it. No car company will list a requirement for premium fuel if it's not expressly needed because it raises the operating cost of their vehicles- an important metric for consumer evaluations.

Cheers,
Dave

 

You said you talked to the"dealer". Who did you actually talk to? If this person is correct then why do they sell Premium gas...so we can feel good about ourselves? I have always burned Premium in my Disco II, but I once experimentedon a cross-country trip with using Regular vice Premium in my BMW motorcyle. I obtained lower milage per tank using the Regular gas.

 

Its not the slower it burns, its less likely to burn under compression until the spark plug sets off the air and fuel mix.
Lower grade fuels can burn under compression much easier with out the spark plug and that is predetonation.

Then its burns hotter and leaves less deposits.

I would be willing to bet that most of the people that the
"Dealer" see's with the deposits tells the dealer that
" O Yes I run the Good Gas" now fix it under Warranty.

The other thing is some people that want to get the best
MPGs never blow out the motor "floor it" to keep it clean.

 

If you run low octane your engine will carbon up. Whoever you talked to, in my opinion, is wrong. The higher octane the better. There is a reason why LR put that stick on your fuel door!

With 93 octance I get almost a 1.5-2 MPG increase and my engine resonds much better. I used 89 octance in early ownership and I will NEVER do that again because I can honestly feel a difference with 93.Besides when I fill up its only$5-8 bucks more to use premium. Personally, I think its worth it.

 

I spoke to a person in the service department at rosenthal land rover in Virginia.
As I said, very suprised to hear his suggestions.

Think I will keep pumping the primium.

He did suggest an induction flush every 30k miles, he was half correct :-)