Premium fuel?

[JohnKel]

Did you mean to say Montrose?

Land Rover National Rally
Montrose, Colorado
August 15-18, 2007

Note to self : Read what you write Yes sir , guess my tongue was over my eye teeth

Cheers
John

 

[Shark_LR3]

If regular fuels are used in high compression engines, detonation can occur which is an explosive, uncontrolled burn. This is like someone taking a mini pickaxe to the inside of your pistons and heads. The pressure wave forces are great and can do physical damage if severe or prolonged instances occur.

Our tech pulled apart a Porsche engine this week with a chip out of the exhaust valve. I suspect detonation - use of regular fuel by the owner to save $$ - to be the cause. Now it's a $2000 engine job.

You can get away with regular or mid grade fuels. I do this too. If combustion temperatures are generally lower (winter driving, cool air, short trips) and you drive like a granny - which is OK that's good for saving fuel. The ECU will ****** timing to avoid engine knock, thereby reducing engine output.

If you are towing, have a lot of load on board, plan on booting it a lot, or it's the summer time - load up on the premium. Detonation can occur without even hearing it.

 

[woodmews]

I use the mid grade 89 with no problem.

 

[roverman]

Shark, this is interesting. I have always thought that if detonation occurred you would hear the knocking. This happened in an old M5 I had and I switched to Premium without hesitation. Fortunately for me, i do drive like a granny, but come summer i'd consider switching to higher grade.

 

[di_LR3_co]

just to stir the stick more.. landrover flatirons (in co) says there is no point in running premium... i have tried both.. and both give me crappy gas milage.. 13mpg on avg. with the wind and down hill helping me out

 

[grommet]

Elevation impacts octane requirements. While I was visiting Colorado Springs & Denver, I was able to use lower octane without impact. Around here (at basically sea level), I do get slightly worse mileage at non-recommended octane levels. Anyway... The engine is designed for higher compression and optimized for 91 octane in most environments.

 

[threeputt]

Grommet is correct. To add, octane is a flame RETARDANT. Most ordinary folk, through the power of the media, believe that higher octane actually causes a stronger explosion in the cylinder, thus more power per ******. Sort of like nitro. Octane actually retards the fire somewhat, and that allows for higher compression without premature detonation. Knocking is that premature detonation ~ the air/fuel mixture igniting before the piston reaches the top of the ******. The piston is still coming up, but now it's fighting against the force of the explosion above it. There is your knocking. As for us hearing it... the better modern engines with ECUs able to compensate are outfitted with knock sensors on the engine block. They detect it, or should do so, way before it is bad enough for us to hear in the cabin, and alert the ECU to adjust accordingly - all in fractions of a second. So yes, you could get away with lower octane fuel, but you are retarding the engine's performance (mileage, power, and so forth) by doing so. Also Grommet's comment about altitude and octane requirements are spot on as well. There is less oxygen in any given volume of air at altitude as opposed to sea level, meaning the air-fuel mixture is less likely to detonate early...thus less octane is required to stay at maximum performance without knocking. Hope this helps....in a previous life I was a SAAB nut, turbo head, and lived 1000' above Denver in Cheyenne, WY.

Jeff

 

[Kestreljr]

I was told that a major reason to use premium was because the lower octane fuels will build up more "junk", I assume carbon deposits, on the cylinder heads and because of the small level of clearance b/w the block and pistons, you will eventually have to have the engine pulled, and the cylinder heads sanded down.

If you don't care about the long-term care of your rover, and or don't plan to keep it into higher mileage, then I guess you could put regular in there and escape dealing with this problem.

But I am no mechanic, just someone who has had this done to his rover for $1,800.

As an aside, I don't know anything about high elevation, but I wish I did! I have been fixated on moving from DC to Boulder the past few months, and I am about to pull the trigger and do it if I keep hearing about the snow they are getting! Forum members: Call me if you need an overpaid marketing/PR employee and you live in Boulder (I guess Denver too!)

 

[BoulderGT3]

I was told that a major reason to use premium was because the lower octane fuels will build up more "junk", I assume carbon deposits, on the cylinder heads and because of the small level of clearance b/w the block and pistons, you will eventually have to have the engine pulled, and the cylinder heads sanded down.

If you don't care about the long-term care of your rover, and or don't plan to keep it into higher mileage, then I guess you could put regular in there and escape dealing with this problem.

But I am no mechanic, just someone who has had this done to his rover for $1,800.

As an aside, I don't know anything about high elevation, but I wish I did! I have been fixated on moving from DC to Boulder the past few months, and I am about to pull the trigger and do it if I keep hearing about the snow they are getting! Forum members: Call me if you need an overpaid marketing/PR employee and you live in Boulder (I guess Denver too!)

Nada. Lower octane doesn't burn cleaner and all the fuels from major companies have the same additives across their line. I am picky about using Shell or the other major oil cos. gasoline. Hard to tell where the thrid parties have bought it and what additives are in it. It's a octane/detonation issue as is well detailed above and the detonation damage is mitigated in most modern engines. The downside of the alititude is a loss of aprox 2.4% HP per 1000' of elevation for normally aspirated engines.

An exteme example of high octane is that in race engines you don't want to run higher octane than you need as it generates more heat which can actually reduce power.

My guess is that there is a "rest of the story" scenario with your friends rover. Dirty filters, an off tune, worn out/wrong plugs, and several other things are more likely to be the cause of carbon and junk than the differance in octane.

I'll keep my ear to the rail for an overpaid PR rep postion.

 

[LakeMaryHSE]

I've only ever used regular (87 octane) with no problems whatsoever. Occasionally, I put a bottle of fuel injector cleaner in the tank to help keep the system operating efficiently.