To answer the question about my driving habits, I drive as often as I can (as my job allows). The miles are spread out through the year. I put 3,000 a month on my 4x4 so I am at Speed Lube often. The price difference between Havoline and Mobil-1 prompted my original question. You want to do what it needs, yet you don't want to waste money that could have bought speed or chrome goodies!

 

The truth is as soon as you change the oil and drive the car...moisture WILL come in. I would change it every 6 months(IMO...you know what they say about opinions). Don't save money by switching to a non-synthetic oil. If cost is your driving factor, change the oil and not the filter. That will save you a couple of bucks. You are not really running the motor enough to contaminate the filter. This is another one of those opinion questions that can be argued from every angle. The best repsonse I have seen was contact a vehicle storage specialist. I change the oil and filter in my boat and FX Turbos before storage then squirt a little engine fogger in the intake while cranking the motor without spark...but that is for a 6 month, non-usage period. You are talking about sporadic storage periods and usage making it hard to give you a straight answer.

 

I change it once a year w/dino oil as I harldy get a chance to drive 1000 iles/yr. Maybe if I lived in a cold climate that got more condensation I'd change it more frequently.

 

Either way, once-a-year oil changes would be a minimum.
I also think that every Corvette should be driven at least 5000 miles a year !! ...just on general principles!!!

Larry
code5coupe

 

Quote:
I have been told that some of the steam from the exhaust you see when the car is cold is some of this moisture "burning" off as the the water will evaporate LONG before the oil will.

Response:
What you were told is incorrect. The steam coming out of an exhaust pipe is water vapor that is a normal by-product of the combustion process. It has nothing to do with water inside a crankcase.


Quote:
Air comes into the engine via a breather system.

Response:
The engine has provisions to vent excess pressure from within the engine. This pressure develops from blowby...the engine has no way of pumping air into the crankcase. An engine crankcase aways has positive pressure, except in the unusual case of an engine with really bad rings that is in high-rpm overrun.


---------------------------------------------------------------------
I reread my post about "Air comes into"....I crossed up two sentences in my head trying to multitask. Totally my mistake.


I had my doubts about the steam from the exhaust. I have a customer who claims to be a retired "GM engineer from the Pontiac Motor Department" that told me that.

 

Once a year or 5000 miles unless you race it or live on a dirt road. I think this 3000 mile bs was invented by the oil companies or jiffy lube placed.

The dealerships are sticking to 5000 miles, and it should stay that way. There's no sense in consuming and dumping nearly twice as much oil.

 

Back in the mid to late 80's the API (I believe) did a study on a few thousand vehicles that ranged from cabs, to delivery trucks, to cop cars, to normal passenger cars, and everything inbetween. What the conclusion was that the oil on some of these vehicles began to fail around 1000 miles, but these were cars that did a lot of stop and go and idling (cabs, cop cars). On some the oil was lasting over 9000 miles before breaking down. These were mostly long distance commuters. Well, the average mileage came in around 3400 miles, so the DIFM (do it for me)industry, which is what I am, picked up the 3000 miles, 3 month rule and made a HUGE campaign out of it. The average oil change interval nation wide is around 4875 ( will get the hard numbers later). At my two stores, the average interval is about 3860 miles. I agree with CENTRAL COASTER, most people can make it 5000 miles, but it depends on your individual driving and vehicle. For customers that have a Cummins, Powerstroke, or Duramax that hold 12 to 16 quarts, I tell them 7000 miles as long as they don't over work it. If you are Autocrossing or running your car hard, get in to my shops around 2500. A $50 synthetic oil change is cheaper than an new LT1.


BUT THE GOLDEN RULE....what does your owner's manual say? The people that designed your car know what is best for it.


As far as dumping, I burn my used oil in both of my stores for heat with Clean Burn heaters. During the summer I recycle it. The US govt is one of the biggest users of used oil. They collect it, filter it, refine it, and use it the military vehicles according to my friends at Valvoline. When the war started demand went through the roof. Companies were willing to pay 50 cent a gallon, but that number has dropped off.

 

I agree...I've been doing this for over 30 years ...even before it ws fationable.1 year or 15K mi.BTW..Mobil one, in the early 70's, used to put on the Can "1 year or 25,000 mi" How many of you remember that?

 

Jay Leno can afford to change the oil in his cars every week

 

dchildress, thanks for the info! I stand corrected.

I think if they measured hours on all those engines, they'd see less of a spread in oil life.

I'm keeping track on my new F150. First oil change at 5000miles was after very mixed city/highway. Put 125 hours on it.

Since then, I've done ALL city miles, only 500 in a month, so I think I might change it sooner.

Sounds like 100-150 hours is a good ballpark. That gives 6000+ miles per change for a 100% freeway car (avg 60mph), and maybe 3000 or even less for an all city car (avg 25mph)

 

I have a new bodystyle Z71. If the key is off and you press the odometer reset button, the current mileage comes up. If you hold the button, the hours on the engine come up. My truck has 165000 miles on it and around 4200 hours!!!! I used to be a millwright/project manager and drove every where. My record for oil changes is 7 in 8 weeks. I own oil change shops now.

BUT the point is hours is the way you track when to change oil in boats and heavy equimpment and I believe that is a better indicator than mileage. I service the local police cars, city vehicles, and fire dept cars (not the big ladder trucks) and I am trying to get them to install hourmeters on new vechicles when they come in. Some of the police cars idle for 5 hours a day!!! THAT is hard on oil.

 

True. 25 years ago, I used to work for a utillity in the shop. They were supposed to change oil every 30 days. When I came I did it every 3 months. The fleet manager (no back ground in vehicle service at all) was always suggesting that was too often because these trucks didn't travel a lot of miles. I always said so what? They run all day. I don't work in the shop anymore, but I do see all their vehicles have hour meters in them now.

 

cause its a waste of time and money.

 

This IS true. That hose on the passenger side of the TB introduces air to the crankcase under most conditions. The exception is under heavy load when blowby occurs most. In that case, the blowby exceeds the capacity of the PCV system, and backs up into the intake.

The PCV system tries to maintain a vacuum on the crankcase to decrease blowby and improve dynamic compression with better ring sealing.

I guess the vacuum would help prevent ring slap?

 

changing oil every 3k/3months is a TOTAL waste of money and oil if you are using synthetic. I change my oil every 6k regardless of time, but its with mobil 1 0w-40

remember folks, Mercedes and porsche use mobil 1 0w-40 in the supercharged and turbo cars, and the oil doesnt get changed for 15-20k oil analysis shows that the oil holds up decently.

www.bobistheoilguy.com learn about lubrication...

even in a normal passenger car 3k is a bit overkill with conventional (dino) oil. Used oil analysis proves it.