Bearings, compression ratio, and gas

[Built_Well]

I was talking to an employee of a Hy-Vee gas station a few weeks ago. Did you know they're regular grade with 10-percent ethanol is now 89 octane, not 87... Usually you only see the *premium grade* with 10-percent ethanol enjoying an upgrade in octane (from 91 to 93).

Hy-Vee's premium octane stayed at 91, but it was nice to see the less expensive regular grade jump to 89 octane from 87. First time I've seen this.

Anyway, the employee of the Hy-Vee station was telling me some interesting info about 93 octane. My '06 Camry's manual calls for 87 octane or higher (regular or higher), but ever since I read Terry Dyson's endorsement of Shell V-Power premium because of the super high levels of detergents in that primo--even more than required by the Top-Tier standard--I've been filling her up with premium 91 and 93-octane V-Power about half the time.

But this man at the Hy-Vee was telling me that if my car didn't specifically require premium, I could actually be causing unnecessary engine wear by using the primo gas 100-percent of the time, or even more than just 30-percent of the time. He said something like the timing and/or compression ratio would somehow be affected in my 87-octane or higher car, and eventually over
time this would take a toll on the bearings.

Well, hearing that a few weeks ago, I stopped buying V-Power or any other primo, and returned to using 87-octane regular--I didn't even fill her up with the 89-octane regular at Hy-Vee. The guy lost a sale by giving me that "info." [chuckle]

Is he right? In order to protect the bearings to the fullest, should I stick with 87-octane in the '06 Camry even though the manual says I can use 87-octane or higher...

 

[Lorenzo]

I cannot imagine a more qualified authority on the subject than a guy pumping gas at the Hy-Vee. I would follow his advice precisely.

 

[Built_Well]

Originally Posted By: Lorenzo
I cannot imagine a more qualified authority on the subject than a guy pumping gas at the Hy-Vee. I would follow his advice precisely.


LOL. That's funny Lorenzo. But this guy wasn't a gas pumper

. He was an older, authoritative-looking fellow who might possibly be the manager, and seemed to have a lot of knowledge about engines. He was going on and on about esoteric engine subjects that I didn't have a clue about.

 

[Tempest]

Higher octane rating simply means that the fuel is less likely to prematurely detonate in higher compression engines. It does not provide more power.

 

[Quest]

Originally Posted By: Built_Well



But this man at the Hy-Vee was telling me that if my car didn't specifically require premium, I could actually be causing unnecessary engine wear by using the primo gas 100-percent of the time, or even more than just 30-percent of the time. He said something like the timing and/or compression ratio would somehow be affected in my 87-octane or higher car, and eventually over
time this would take a toll on the bearings.
[chuckle]

Is he right? In order to protect the bearings to the fullest, should I stick with 87-octane in the '06 Camry even though the manual says I can use 87-octane or higher...


*yawn*
In the house of idiots, nothing comes close to trusting a gas bar attandent about gasoline engine octane rating and operations. No wonder our technological progress is falling behind (ha!)

If your car is spec'ed to be 87 octane (RON+MON divide by 2), you can certainly use anything that is 87 or higher (higher doesn't necessary means better so long as your engine doesn't require it due to reasons). While some older cars may require higher octane gas to run smoothly (the catchword is "smoothly") due to accumulation of deposits over time, most vehicles do not need anything higher than spec'ed.

AS for higher octane gas damages bearings, I think that gasbar attandent should be slapped silly and be banned 100ft from coming close into contact with his clients, gas jockeys, parents who own gasoline-powered vehicles, or even general motorists.

 

[GR8]

I consistently get 1.5-2 more mpg with premium. Drives noticeable different when wife/children refuel with lower octane, vehicle is a 1999 ford crown victoria.

 

[addyguy]

I'm not an expert, but two things come to mind:

a) Engine computer adjust to accomodate the octane level I thefule pumped into the tanks, AFAIK. So the engine would adjust to ensure nothing bad happens.

b) Even if the engine didn't adjust, the amount of 'extra power' a higher grade of gas would give, when spread out over the 'load bearing surfaces' in the engine shouldn't be enough to cause any damage to the engine. Engines, these days at least, are built to take a lot of use and abuse, including 'changing circumstances'...I wouldn't worry about it!

 

[INDYMAC]

Some fuel additives can cause adverse effects on bearings (leaching). This is more noticeable on UOA's where fuel dilution levels of oil are above .5%. Since premium grades of gasoline normally contain higher levels of cleaning agents, I could see where this well intentioned gas pump attendant got a little confused about the "bad for bearings" explanation.

As an anectdote, I can tell you that Shell V-Power has considerably less leaching effect (Pb) than Chevron Supreme in two of my vehicles that have fuel dilution issues. My third vehicle does not have a problem with either brand, but it also has little to no fuel dilution of the oil.

So, there's my $.02.

 

[OVERKILL]

Originally Posted By: GR8
I consistently get 1.5-2 more mpg with premium. Drives noticeable different when wife/children refuel with lower octane, vehicle is a 1999 ford crown victoria.


For engines that run "on the ragged edge" in terms of self-tuning, the knock-sensor is used to adjust the timing so that under cruise and part-throttle load, it can use the most timing (which typically gives you more power) before pre-ignition occurs.

When you increase the resistance to detonation of the fuel, you increase the amount of timing the ECM can throw at the engine before the knock-sensor says "whoa boy!", so it is very possible to see these types of gains.

It is dependant upon the engine and computer though.

On a carbureted vehicle, or an older computer-controlled vehicle that lacks a knock-sensor, the advantage of this scenario does not occur.

My Town Car AND my Mustang/Capri both require higher octane gasoline. The Town Car is due to the increase in compression of the milled heads; it pings on anything lower than 91 octane even at the stock base timing setting of 10 degrees. The Capri is running 15 degrees base. The latter is a scenario where a person has KNOWINGLY increased the base timing to take advantage of higher octane gas. It would run fine on regular at the stock timing setting of 10 degrees, but would lose power.