I had an independent shop go the other direction–they put in 5W-20 when the car called for 5W-30. Since it was cold weather and the car was used mostly around town, I ran it until the next oil change. I had no oil consumption problem. On the last oil changes,the shop put in 5W-30 synthetic oil which isn’t required by my owner’s manual. I think that the shop buys 10W-30 in bulk and doesn’t really want to put in any other kind of oil. For years I changed my own oil and I’m about ready to back to doing in myself again.
That’s why I do it myself. I KNOW that I’ll do it right with the correct oil.
when i was working for good year this man brought in a 1985 chevy citation 4 cyl he was from flordia and requested 15-40.He bought the car new the day he got it he said he changed the oil to 15-40. This was the first for me.He said if it is warm where you live and doesnt get cold you wont have a problem. So i made up the work order and went to change it. I drove the car into the stall went to record the miles WOW 368,000 i never seen one of them cars run this long.The crazy thing is it sounded like it was still new. My wife had the same car and i put 5 motors in it built the 6th and put a kill switch in it LOL (She better carry oil with her at all times) the light comes on the car dies no matter where she is… Solved my engine replacement problem…
15-40 is universal fleet oil, rated for gasoline and diesel engines. It’s safe to use in everything from lawn mowers to turbocharged diesels
15W40 is not a specific oil, it is only a measurement of the weight of the oil over a temperature range. Any specific 15W40 oil may well be rated for gasoline and diesel engines, but it would not be acceptable in my car’s diesel engine nor in many gasoline engines.
I will repeat my comments, Heavier is not always better or even acceptable for many uses. Being rated for diesel or gasoline does not mean it is rated for [b] all [/b] gasoline or diesel engines. Consult your owner's manual for the specifications for the oil needed for your car.MikeinNH, you are right about changing your own oil. For years, I did much of m own maintenance, but in recent years, my job has been so demanding that it is more convenient to have my vehicles serviced by someone else. As you can see from my other post, the independent garage that put the 5W-20 in when I requested 5w-30 put in synthetic oil this last time that I did not request. The claim was that 5W-30 was only available in synthetic which I know is bogus. On my Toyota 4Runner, the Toyota dealer put in 10W-30 instead of 5W-30. The owner’s manual of the 4Runner does say that 10W-30 may be used, but to return to 5W-30 at the next oil change.
The independent shop claims that 10W-30 oil is really better for most applications. My guess is that both this shop and the dealer probably just get 10W-30 oil in bulk and put it in everything. I had had good luck at the independent shop, and had even recommended this shop to others, but I’m about ready to change shops. By contrast, the Chevrolet dealer where I bought an Uplander has always put in the correct oil and charges less for the oil change than the independent shop.
The ONLY situation where 15W-40 fleet oil might cause a problem would be if the vehicle sat outside in BELOW ZERO temperatures.
Here in Mexico, there are 4 grades of motor oil. 30, 40, 50, and 20W-50. Late model Fords (which are built in Mexico) are labeled 5w-20 but they somehow survive without any lubrication related engine failures with a crankcase full of straight 30.
The only damage to an engine that could be traced to the lubricating oil I have ever seen was when there was NO OIL in the crankcase or it had literally congealed from not being changed for 10 or 15K miles… In my opinion, substituting 15-40 for 5w-20 in a mild climate will not cause any engine damage or problems…
The other designation, such as “SM” determines if the oil meets the manufacturer’s requirements for that engine. Even heavy diesel manufacturers often have their own spec, such as Caterpillar, Mack, Mercedes. etc.
The viscosity figure is determined by the operation environment; ambient temperature, engine loading, turbocharger, trailer towing, etc.
Engines that only start infrequently, such as locomotives, use a straight SAE 40 viscosity for best results. Such engines are started in the winter indoors, or the oil is preheated!
The thing that would concern me more is how would a jiffy lube run out of bulk oil? Must be poor management. Anywho, no the 15w40 oil will not hurt your car, its really not a whole lot thicker than 10w30 or 5w30. just put the right oil in it next time around.