FAQ: Engine Oil - What type and change intervals?

I found this while surfing online. Interesting reading, but it's from an oil company, so take with a grain of salt:

Quaker State Tech Bulletin T-1007 B: WHY CHANGE CRANKCASE OIL?

How long can motor oil be used without changing? This has been a popular question ever since the early days of the automobile. Developments in the past few years have made this question even more prevalent.

Many motorists are now asking: “With all the advertising about new and improved motor oils, why can’t they be used a lot longer between drains?”

Other questions involve the many varieties of crankcase “gadgets” which are on the market. Some of the “gadgets” are claimed to neutralize acids, and others to prevent oil oxidation or deterioration, with claims that motor oil can then be used from twenty-five to fifty thousand miles or even with no oil changes at all!

Quaker State Motor Oils are fortified with inhibitors to give them remarkable stability and resistance to oxidation and deterioration. They also contain acid neutralizing additives to eliminate any fears of acidity or engine corrosion.

Quaker State Motor Oils won’t break down, or wear out, or become acid under normal operating conditions in a passenger car engine. So why bother to change oil? Unfortunately, the answer to this question is not short or simple.

Motor oil must perform two primary functions. It must lubricate the engine, which is obvious; but it also has to serve as a collector of contamination. Summed up in a few words, good motor oil won’t wear out, but it can be contaminated to death. So the question is: What is this contamination and where does it come from? T comes from the engine combustion chambers where the gasoline is burned to produce powder.

We’re faced with two different types of fuel combustion in engines: efficient combustion or clean burning; and inefficient combustion or dirty burning. If you’re old enough, you may remember the kerosene lamps your grandmother used, or maybe it was your great-grandmother. Anyway, if the lamp wick was trimmed and adjusted properly, she got a clean, bright flame; but if the wick was ragged and scorched or turned up too high, the flame was dull and smoky and the lamp globe quickly became coated with greasy soot. Strangely enough, these same differences exist in engine combustion chambers and have a vital effect on the crankcase oil.

But just as a modern engine is a lot more complicated than an old-fashioned kerosene lamp, so is this problem of dirty burning in engines a lot more complicated. When dirty combustion occurs in engines, soot isn’t the only thing formed. Sticky, gummy products, which oil chemists call resins, and lead oxyhalides. Small quantities of acidic combustion products are also formed. Last, but by no means least, is water. For every gallon of gasoline burned, a little over one gallon of water may be formed, believe it or not! So during the burning of gasoline in engines, we have a potential problem with soot, resins, acids, and water which are formed. If these combustion products work down past the pistons to get into the crankcase oil, then we do have the problem of dirty, contaminated oil. If the oil is allowed to become too dirty and contaminated, sludge deposits will form to cause plugged piston rings, oil pump screens and oil filters. Engine wear and even engine damage can then result.

So now you may ask, “When does dirty combustion occur, and when does the contamination work down past the pistons and get into the oil?” The answer is when the engine is cold. An engine used in typical city driving with a lot of short runs, stopping and starting, seldom gets a chance to warm up thoroughly and operates at its lowest efficiency, which means dirty combustion. The cold cylinder walls of the engine act as condensers for the soots, resins, water and unburned gasoline. These are washed down past the pistons into the crankcase oil. An engine has to have a good, steady run before it is thoroughly warmed up, and a considerable longer time in winter. The first few minutes after each cold engine starts is the hardest on the oil.

After an engine has been run long enough to get thoroughly warmed up, it’s then operating at its best efficiency, which means clean combustion and a minimum of combustion soots and contaminates. Furthermore, the hot cylinder walls no longer act as condensers, so the contaminates are minimized and don’t work down past the pistons into the crankcase oil.

Contrary to popular belief, a truck, bus or passenger car driven at highway speed on a long trip is the easiest job to lubricate and the least demanding on an oil of good quality. The really tough lubricating job is the engine, which gets only short runs with lots of stops and starts, especially in cold weather.

Did you notice something? The worst conditions for both the engine and the oil are the very conditions under which the great majority of passenger cars are used most of the time.

Oil changes are necessary, not so much because oil wears out, but chiefly to flush contaminates from the engine before they build up to dangerous concentrations.

If a car is used for a lot of steady cross-country driving, where the engine runs hot and efficiently, a good oil can be used for 7500 miles and longer. But, if a car gets most of its use in town with many cold starts and few long runs to get it really warmed up, then oil changes every 90 days are good life insurance for the engine, and that’s especially the case during winter driving. Maybe a car owner can get away with using oil longer, but after all, oil is pretty inexpensive when you consider the important job it has to do. One engine repair job can cost a lot more than all the oil needed for several year’s safe lubrication.

CAR MANUFACTURER’S OIL CHANGE RECOMMENDATIONS

Most car manufactures recommend oil changes at the end of a specified mileage or after a certain time interval, whichever comes first for specific driving conditions. This type of recommendation permits the high mileage driver who operates his car under favorable conditions to change oil at fairly high mileage intervals. It also insures that the stop-and-go type of driver who operates his car under unfavorable conditions changes oil at regular time intervals before contamination becomes excessive.

At improvements are made both in engine design and lubricant formulation the car manufactures extend their recommendations. With specially formulated oils such as Quaker State Sterling Motor Oil even longer drain intervals are possible and the car manufacturers will be recommending longer drain intervals when oils of this quality are used.

Makes me kinda glad I've changed the oil every 3k miles since I bought the car.

i never hit 3k in the 4months i go between changes. my oil looks almost good enough to put in another car lol.(thanks mobile 1 and PF52 filter)
btw it is surprising how many people go into the auto parts store or to a service shop and are shocked that they have to change the filter too!
its funny hearing some woman say " what?, i have to replace the filter too, but my car is almost new!?" i know back durring the early car days you could use the filter for 6k miles and change out the oil every 3k, but the cars had monster filter back then...have you seen a camry's oil filter?!? it looks like its for a go-cart. :roll:
i felt sorry for those people who brought their cars in for the yearly oil change because they didnt have time or felt it wasn't that important. to know their engine wouldnt last another 2 years
running a quart low, nail in the tire, no pads left, and a factory air filter in a 5yr old car... some days i just had to shut my mouth, hand them their keys, and say see you in five years

I don't get the part with one gallon gas burned could mean one gallon water formed. Sounds a little incredible no matter where that water goes

yea that sounded a little funnny to me too, it almost defys physics. 1+1=3 !?!

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I don't get the part with one gallon gas burned could mean one gallon water formed. Sounds a little incredible no matter where that water goes

That's because when your burn the gasoline, you are combining it with air.

Gasoline is a mixture of lots of different hydrocarbons (such as octane, C8H18), but a typical reaction would be

2 C8H18 + 25 O2 --> 16 CO2 + 18 H2O

Notice that every molecule of gasoline produces 8 molecules of carbon dioxide and 9 molecules of water. It's also important to note that oxygen weighs more than carbon and a LOT more than hydrogen. That means that most of the stuff in the combustion products (by weight) comes from the air, not from the gasoline.

That's how you end up with a gallon of gasoline producing a gallon of water--because for every pound of gasoline you burn, you are combining it with several pounds of oxygen from the air, and the result is several pounds of CO2 and several pounds of water vapor.

I was gonna say that!

2 C8H18 + 25 O2 --> 16 CO2 + 18 H2O

OMG we just did balancing equations in Chemistry today WOW

what do most of you guys use for oil in your Riv's? I use castral gtx high mi. 10w30.

10w30 Valvoline (non-synth) for the last 105k miles.

how often do you change it. i do it a/b every 3,000 mi.

Mobil 1 Extended Performance

Mobil 1 or Havoline Synthetic with K&N performance filter every 5-7k miles.

Every 3k on the nose for me.

I know synthetics work as they say, but I'm not keen on the idea of using the same oil for 5-10k miles (or even 15k!!!). Even if the oil doesn't break down, there's always the chance that some foriegn matter, debris, metal from engine wear, etc. could get into the oil and cause damage, especially if using aftermarket internal parts. You just never know.

If I was really loaded with money, I'd do synthetic every 3k miles.

I use royal purple full synth but is FOR sure do mine ever 3000-4000 still

I use Valvoline Durablend 10W30.

M1 10w-30

Everyone using the larger PF52 filter? Didnt check, but Im sure it is in the oil faq. I just started running Mobile1 in my daily driver riv. Plan to change it at 4500.

i used to run GTX 10W30 w/PF-52 filter and i changed it every 3k or 4 months(sometimes it was only 2500miles after 4 months).
i recently switched to M1 10W30 with the PF-52 delco filter. i will probably let it go for 6months or 5k miles, since it is syn and i dont drive much. FWIW i didnt notice any power diference between GTX and M1.
the most important thing is to change it out every 3k and use any filter except fram!

btw i have never let anyone else change my oil, i just dont trust other people . no one but me has even driven my car, except my dad one time around the block to feel the brakes when they were bad, oh and the ocasional mechanic if they refuse to let me drive it into the bay.

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Even if the oil doesn't break down, there's always the chance that some foriegn matter, debris, metal from engine wear, etc. could get into the oil and cause damage, especially if using aftermarket internal parts. You just never know.

You're directing your worries to the wrong element. True, foreign matter, debris, metal from engine wear does get into the oil sythetic or not. The FILTER is the weak link in the chain, not the oil. Use quality filters and you won't have the debris floating around the oil. Stay away from FRAM... if you use it, your just as good off using no filter. Fram is junk.

Synthetic oil does not break down like petroleum based oils over time and use. Syn oil also lubricates engine parts faster during cold starts when most damage is done. If you're unwilling to do oil changes in excess of the 3k mark, don't use syn oil. Even cheap petroleum based oil last that long.

Numerous tests have been done on synthetic oil and petroleum oil and the proof is in the pudding. Syn oil is hands down more effective in protecting your engine from wear. It's the filter that determines for how long and how well.

valvoline maxlife 5w30 fram tough guard filter every 3k up to this point

Just now changed oil+filter, mineral oil Mobil 10w30, next will be in 3000 miles

M1..in engine and trans... chan engine every 6000,,filter every 3000 use either AC..or M1 filter....

Presently have 105,000 on my 97 s/c. Previous type unknown when I got it at 70,000, did not want to risk seal failure and all that goes with a change to synthetic at high mileage. I have been using Penzoil high mileage 10-30 and a big wix filter for years and changing both at 2500 religiously.

Synthetic oil does not promote seals to fail that I'm aware of. The molecules of synthetic oil are smaller, more consistent in size and less apt to cake up so it' may be more prone to find ways to leak out around seals that were already marginal though. That's why people who switch to synthetic claim it causes seals to fail when in fact it doesn't.

btw... wix and AC are highly rated filters for performance and filtration.