Engine oil question

[Dawes]

My Ford Ranger ( 4 cylinder inline engine) calls for 5W-20 engine oil. The factory knows far better than I, but it just seems a bit thin to me. Is there any reason that this grade would be more desirable than, say, 10W-30?

 

[ivymike]

the 5w-20 oil is primarily intended to provide improved fuel economy vs the more conventional 5w-30.

I suspect that many of the smoking vehicles you see are owned by people who would gladly save $20/yr by skipping oil changes, or who never check to see whether their oil is getting low. I wonder how long they go between changes - 15,000 miles seems very "doable" with synthetic (mfr recommended interval on some newer cars), and "natural" oil seems to hold up well into the 7000mi+ range.

 

[franzh]

I agree that modern engines have better tolerance control then older engines, and work just as well with lighter viscosity oils. One additional item to ponder, lighter weight oils also have less drag and can provide a measurable improvement in fuel economy. Here in the deep south USA, we tend to use the heavier viscosity oils, as allowed in many of the owners manuals. My auto manual states that it requires 5W20, I routinely use 10W30, but I also like to use semi-synthetic at 5,000 mile intervals.
Finally, as to "Enginebobs" comment about late model cars with oil controls, I frequently visit the dyno labs at a VERY modern engine research facility, and also review the emission results. I almost never see a smoker there, and if I do, the emission results are way out of range. Oil control is not such a problem as it has been in the past. The "smokers" tend to be from high mileage autos which have had less then ideal service, abused, poorly maintained, etc. A recent comment overheard at a manufacturers conference relayed this: "Our engine warranty's due to oil consumption is almost nill". A quick look at vehicles which have failed roadside emission tests reveal my previous comments to be true, and also, a very high number of them with "Check Engine Lights" illuminated.
The auto of today is without a doubt better built than those of 15 years ago, or even 10 years ago.

Franz

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[Tmoose]

I am no fan of changing engine oil more than is necessary. The Consumer Reports taxi test of more than a decade ago, and my experiences with Volvos, and an online test of synthetics in a Camaro ALL make 7500 mile oil changes seem very reasonable for nearly all cars.

Last year a friend of mine told me about a major engine problem he had with a Dodge Intrepid that developed heavy sludge deposits despite proper oil changes. Despite his engineering background I silently questioned his story.
It turns out his experience is not unique, and Toyota and VW and Audi are facing similar problems.

http://www.cleveland.com/business/plaindealer/index.ssf?/base/business/10936855867650.xml#continue

There may be situations that make engines of different makes more vulnerable than others, but I'll be keeping an eye on oil appearance while continuing extending the oil change interval. I have to decide how silly I think it is to be scared for my old Volvo IF Toyota's problem is inadequate crankcase ventilation. Then there is risk VS fear, the age old insurance question.

 

[patdaly]

Dawes, as others have mentioned, engines today are a far cry from what we had years ago. Another point to consider is the very different tolerances held within modern engines, and the possible repercussions of running a too heavy oil. One very real repercussion would be decreased flow across the bearings. As engines advance, companies are reducing clearances, and gaining the ability to run lighter oils. When we add the heavier viscosity oil, the pressure shown on the gauge may go up, but the actual flow rate across the bearing may drop below what is needed to remove heat from the bearing, and can cause bearing failure. Now, I would say there is a margin involved, and 10W30 "should" not cause a problem, but what do you gain by not following the Mfg. recommendations?