Regular Or Premuiem Gas?

vanity | Feb. 24 2003 | self

[ez]

I ran a spreadsheet one time and I entered all my miles, gallons, and price of every tankful for about two mos, and if you take it down to "cost to drive one mile", there is virtually no difference between Regular and Premium, due to slightly increased mpg's for Premium.

Therefore, one should follow manufacturers recommendations without reservation.

I run 87 in my Frontier cause the book calls for it, but I ran 93 in my 240SX with the same engine. Go figure...

[oceanperch]

Both. My son is 6ft tall and cannot duck getting in and out of the van.

Dropping the floor and raising the roof for clearance. Also I can walk around without bending over to work around the chair. First van was a Chevy Astro long time ago and walking around bent put strain on an already strained back.

He is getting a new chair with smaller wheels lowering his height so that will help.

The Ford I moved the gas tank and was able to drop the floor. The Chevy van did not have a conversion kit for its gas tank.

Hope that helps.

[jiggyboy]

A few minor points not already covered:

- Check in your owner's manual for the type of gas that is recommended for your car. They will come right out and tell you that it should be, for example, 87. Re your #14, different cars come with different recommendations. You're not giving your car a yummy treat if 87 is recommended and you give it 89 or 91.

- 3,000 miles between oil changes is the rule of thumb; I have done very well indeed by going by the recommendation for my particular car, which has been 7,500 miles for two different cars. It saves me a marginal amount of money and time. This might also be in your owner's manual, might not, but would definitely be found in a "Haynes" repair manual that you could get at most auto parts stores for like $15.

- I have also done very well with cheap, no-name gas vs name-brand gas. Mileage is the same, engine life can't be beat (210K and 150K so far).

- I have heard what sounds like a lot of BS, mostly from auto dealers, that Arco gas (it contains some methanol) beats up the rubber in the engines of new cars. This, based on a one-car sample of 75K miles, is demonstrably BS.

- "All filters" includes the air filter, the fuel filter (sometimes 2), PCV valve, etc.

- Check your radiator, tires, and oil about the time you fill your car with gas. You'll determine pretty quickly whether you've got a leak in any of those systems.

[Burlem]

I listen to Dr. bill Wattenberg on week-ends. His partial resume is: Research Scientist, Professor of Sscience, Consultant to Livermore National Lab, Staff member of physics division of nuclear weapon design.
I tell you this so you know he is of crdibility. He said that if you buy the high octane you are wasting money. There ARE some high performance cars that need this gas, but the average persons car can do well on regular. I have a 96 Crown Victoria, the book susggested the medium grade, when I heard Dr. W, give this advice, i switched and had no problems.
You can try the lower grade, he said if it pings too mcu then go back but in the majority of cases the car will be fine and you will have more money in your pocket.

[ScholarWarrior]

Both of my Jaguars require premium. Even says so on the gas gauge.

[Johnny Gage]

One thing I recently learned about reg/prem gas.

According to several 'small egine' dealers:

If the lower grade gasolines have ethanol in them (like in Minn.) you will want to run premium gas in all your small engines. (mower/chain saws/atvs etc.)

The reason is that the ethanol can cause damage to the alloys used to manufacture the blocks/pistons etc.

Just my 2.9 cents. As with things like this YMMV.

[WFTR]

As others have said, "octane" is a measure of how quickly the gasoline burns. Ideally, you want an even burn and even expansion in the chamber for the entire piston stroke. If your gasoline burns too quickly (has too low an octane), it finishes burning and expanding while piston is still moving towards its most open position. The expansion from other cylinders must then force this piston to complete its movement. If your gasoline burns too slowly (has too high an octane) then you are losing fuel value to the exhaust.

Generally, higher octane is attained with heavier hydrocarbon molecules and with branched molecules. Refineries have special units to produce these molecules from smaller, lower-value molecules. Sometimes, a higher octane gasoline is better in the summer because it will not evaporate from the tank as easily. Likewise, some people have used lower octane gasolines in the winter because the smaller molecules flow better under cold conditions. In many states, the government forces refineries to make some of these seasonal adjustments within an octane rating.

The difference between gasoline brands is typically only a difference in additives. Naphtha is naphtha is naphtha regardless of who refines it from crude. The secret is in what they add.

WFTR
Bill

[oceanperch]

Yeah OK.....Thanks..

[oceanperch]

How come when you explain it its actually more fun to read over and over.

Dry as it is it still has some teaching qualities.

You sure your not my old English turned Auto teacher....thanks for the help....

[oceanperch]

Thanks for starting the discussion.

[Myrddin]

Thanks for starting the discussion.

I've learned a few things in this thread too :-)

One note regarding additives. I bought a 1974 Porsche 914 when I was in San Diego. I made that purchase in 1989. Shortly after I bought the car, California mandated the addition of MTBE in the winter months. I have had to spend over $500 on two occasions to replace all the rubber, the fuel pump and the pressure regulator in the car. My last "tune up" to pass California smog cost me $1200. The car is now garaged in Idaho. No more MTBE fuel and thus far, no evidence of fuel system damage.

[null and void]

Is it just a lure for people who think their Geo Metro will really have more oomph with a little higer octane?

Pretty much.

[azhenfud]

Really - economics make the difference negligible for me. I use the high octane.

My case is(was) like this:

16 gal tank @ 18.125 mpg x 1.749/gal regular @ 290 mi range/tank = 0.0965 cents/mile

16 gal tank @ 19.755 mpg x 1.949/gal premium @ 312 mi range/tank = 0.0986 cents/mile

I'm to the opinion the octane/mpg is calibrated by the oil companies to net the same - regardless. But, you do the math on your own experience and see....

[Petronski]

In general, you should use the lowest octane which the manufacturer recommends. If you have engine knock, you should try the next higher octane level until the knock goes away. Then continue to use that octane level.

These 'premium' 93 octane fuels offer no benefit to an engine not tuned to take advantage of them.

[CDHart]

Can you tell me why the manufacturers of newer cars recommend using 10W30 oil instead of 10W40? It seems to me that the 10W40 would be better protection for the engine.

Carolyn

[oceanperch]

Thank you all for such great responses.

[oceanperch]

Math! Now I really have to think. LOL Thanks for another perspective.

[oceanperch]

I live in Oregon (no self serve) and our fuel is still cheaper than our neighbors to the South.

The price recently went up and at the same time legistlation is trying to turn our law over to "self serve"

I like service because someone is tending to the van where my son waits while I take a potty break re fill my Cola. I also travel with both of my adult Labs who secure the inside of the van. Labs are great security and they only require the $1 menu and doggie duty breaks at the rest stops or behind office buidings after hrs.

[Publius6961]

Buying a higher grade than required is a waste of money.

Not quite accurate. it goes beyond wasting money.
I happen to be in the market for a new car and am looking at a hybrid (Toyota Prius) for commuting. I have been visiting as many web sites as possible to familiarize myself with the differences and new service requirements and technical nuances that go with the new technology.

Among the problems I found discussed is a strange one where the owner could not achieve the mileage the car is capable of, and it turned out to be that the octane of the fuel used was too high.

The difference in volatility was upsetting the programmed timing and totally destroying the efficiency designed into the engine.

[oceanperch]

I am going to start looking at octane levels now that you all have educated me on the subject. :)