Re: Automakers Lengthen Oil Change Intervals

On Tue, 27 Mar 2007 18:07:37 GMT, "Speeders & Drunk Drivers are


"Engines last forever if you change the oil frequently". Where did you come up with THAT?
For all you frequent oil change advocates, keep in mind that MOST engine wear occurs after cold starts, when the bearings and other surfaces are relatively dry of oil.
You can change the oil at 100 miles intervals and you won't reduce the wear from cold starts.
Lots of testing has been done over many years which proves that.
About 25 years back, Popular Mechanics mag did a review of a gizmo system that prelubed cold engines by pressurizing the oil gallerys via an electric pump and a timer that delayed ignition during starts until all oil passages were pressurized. However, it was fairly complex and most owners wouldn't want to be bothered.
Some heavy truck engine makers have tried the same thing and so do some maritime engines.
One reason why taxi and other fleet engine use achieved high mileage before engine teardowns is simply the fact that the engines are started once a day and never shut off during the hours of use.
BTW, in maritime HEAVY diesel applications, under conditions far more severe than auto useage, oil is NEVER changed.
I've served about ships with huge 4 story high 38,000 HP slow speed diesel engines. Lube oil is distributed by separate pumps from a huge reserve. The reserve is replenished as it drops by pumping in new oil.
The oil is purified after it passes thru the engine by being slung at high speed in centrifugal oil purifiers where all solid matter is spun out. At 30 day intervals, samples of lube oil are sent to a laboratory for analysis. the amount of bearing material suspended in the oil is noted to determine wear rate of the engine. The lab recommends additives as necessary and the oil is continuously used.
The bearing loads in these engines are astronomical compared with auto engines. There's nothing like seeing a 5 ft diameter piston going up and down in a 15 ft stroke,with an output power of 5,000 HP per cylinder... The internal cylinder pressures are extremely high since these engines are also turbocharged. There nothing like those turbos screaming away in the engine room. Their sound level is up around 135 db's. Ear muffs are neccesary or you go deaf in minutes.
Doug
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