Dumb question:How do I switch from 5w-30 for 10w-40?

As I said in the third post. He was going to open a can of worms.

Not his fault – he got everything he needed in the first three replies. Then the know-it-alls woke up.

Auto parts and big box stores have run out of shelf-space for motor oil and all the other automotive lubricants needed today…They can only stock a FRACTION of what is on the market, they just don’t have room for it all…

So the time is ripe for a chain of “Lubricants Only” super-stores, devoted to stocking the complete range of run-of-the-mill and specialty lubricants today’s car owners think they need…You might as well add a “Farm Lubricants” aisle, stocked with 5-gallon buckets of diesel oil, gear oil and hydraulic fluids formulated to meet the dozens of different and often conflicting specifications churned out by equipment manufacturers…

Lets see…After the 200 yard long Automotive aisle, the diesel truck aisle, the Motorcycle / ATV aisle, the Marine Lubricants aisle, the Farm Equipment aisle, the aviation corner, the racing lubricants section and the spray-can aisle,…Did I forget anything??

Well, it’s nap time…

Thanks for the chuckle Rod.I think I’ll take a nap too. We know-it-alls have to stick together.

The pressurized oil system on my 19HP and 20HP Kohler engines in my riding mowers recommend straight 30 weight as well as the Briggs and Stratton and Tecumseh engines on my push mowers.

Mine do too. I was only suggesting another POSSIBLE use for the discount oil. As with cars, owners of powered equipmeny should follow their manufacturer’s recommendations.

I found this very interesting.

http://www.lycoming.com/support/publications/service-instructions/pdfs/SI1014M.pdf

Interesting. I bought some 5W30 at a fleamarket last week. Can I just go ahead and use that in my Lycoming instead?

Look in your owners manual again. I think you will find a chart that looks like a thermometer and beside it will be several arrows covering a range of temperatures. Each arrow will be for a particular viscosity of oil. for example, there would be an arrow that goes from 0°F to over 100°F for 5w30. Another arrow might go from 32°F to over 100°F for 10w30 and 10w40 etc. 5w30 covers the temperature range for most og the lower 48.

Keith, were you responding to me? My post was meant as a joke response to Rod’s link. It doesn’t work that way with aircraft engines. It must be correct. And able to be signed off by the FAA inspector. If the engine sputters and dies one cannot simpl[y pull to the side of the road and call AAA. There are no soft shoulders at 20,000 feet.

No, I was responding to the OP and anyone else that might be interested. The chart I spoke of will give him his answer, I don’t know where he lives so I don’t know his climate conditions. If his climate temperature extremes fall within the range bar for 10w40 oil, then he can use it. When I posted this, I didn’t realize there was a page two so I didn’t see your post, but now that I see it, I get it.

Cool. Have a great weekend.

Here’s the real story about oil, as it was explained to me by an aircraft mechanic, whose name was, as I recall, “Buzz”. Buzz explained that automotive multigrade oils are a mixture of a petroleum base stock of low weight and a vicosity improver which he described as “basically glorified STP”.

Since multigrade oils start out with a petroleum base equivalent to the lowest weight number, it stands to reason that 10W-40 oil must have more “glorified STP” and less petroleum base in it than 5W-30 or 10W-30 oil. Which means, I my opinion, that it might not be the best idea to consistently use 10W-40 oil, which was formulated for use in pre-1980s cast iron engines, in a later model alloy engine.

Still, I would not worry about using some of the 10W-40 oil in a standard performance engine. You can use it for topping off or or mix a quart in with the correct weight when you change oil. If your winter weather is extremely cold (under about 20F overnight) you should not use it in the winter, however. If you do have some 10W-40 in there and the engine and engine block temperature is under about 40F, let the engine warm up a little before you drive.Mixing oils is not going to prevent the oil from functioning as motor oil.

If you vehicle has a high performance or custom engine, follow guidelines exactly. Once you use up your 10W-40 oil, get the right oil next time. You can use 10W-30 oil in a old cast iron engine. 10W-40 in an alloy engine is not the best idea.

In any multi-grade motor oil, the base stock oil’s viscosity is ALWAYS less than the lowest viscosity rating…In other words, the base oil used to make 5w-30 is thinner than 5 weight oil…That oil is made to ACT like a 30 weight at 250 degrees by the magic of STP type additives…

Viscosity modifiers are NOT similar to STP additives. Viscosity modifiers are microscopic coiled poloilymer strands suspended in the base oil that uncoil and expand with heat, adversely affecting the oi’s ability to flow (making it act like a higher weight at elevated temperatures).

STP makes a number of additive products, but they’re commonly associated with an additive of theirs that’s basically a heavy weight oil that “blends” to make whatever’s in the pan a heavier weight. The additiive they’re known for is not a viscosity modifier.

And there is an important difference. STP additive is a lubricant. Viscosity modifiers are not. That’s why it’s recommended to never go beyond a 30 spread between the base weight and the higher number. The more viscosity modifiers added into the base oil is the less lubricating ability the mix will have.