question about oil weight vs oem

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385
Location
Montreal, canada
Hi guys, I'm learning a lot from you and I have a question that I'm sure a lot of people here are afraid to ask: If my car calls for a 5w30 weight oil and I put a 0w40 in it, let say to reduce oil consumption, what's happening inside my engine? Is there going to be be more wear? Is my car going to start some leak because its too tick? Is the engine going to die sooner? I'm just asking, I searched a lot here and couldn't find the answer. Thanks! -Mark.
 
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Messages
4,998
Location
Milwaukee, WI
No, none of that. You're definitely going to get worse fuel economy. With some cars, the variable valve timing can be thrown off, but that's pretty rare and AFAIK only a problem on some of the Ford I4's. But no more wear. No random leaks. No dead engine. The 40 weight is nowhere near as thick as the 30 weight is when your engine isn't up to temp. I'd probabably try a high mileage oil first. They generally have more seal conditioners to try to plump up the rubber/plastic and stop leaks. Do you know where the leak is coming from? As always, a little info about the engine and oil would help. 0w-40 sounds like a syn. Have you considered Rotella 5w-40? Cheap, available in bulk....
 
Messages
9,568
Location
Ontario, Canada
Well if your engine clearances are getting bigger I would run thicker oil to keep the oil pressure up and reduce the chance for metal to metal contact. Really even 20W50 isn't that much thicker at operating temperature than 5W30, I doubt you would notice the difference pouring them into a container by hand. There will be no more wear(maybe less) and probably a slight reduction in oil consumption with running thicker oil. What's the problem with your car? Ian
 

Spykem4e

Thread starter
Messages
385
Location
Montreal, canada
I have a 2005 cadillac cts with the 3.6l v6 vvt with 106k miles on the odo. I used to put in the engine Mobil 5w30 and oil consumption was about 1qt per 4k-6k miles depending on condition. Seems normal to me. Then, I switch to M1 10w30 (I couldn't find any 5w30 anywhere, even from pennzoil) and the car started to consume 1 qt per 800 miles. I switched to Pennzoil platinum 5w30 and now I have almost 2500 miles on it and on the oil dipstick, its half a qt needed. I have a small seepage from timing chain cover gasket (no oil drop, just a really small seepage) and I'll change the valve cover due to a small seepage from there too in about one month. But even with those 2 small seepage, the car used to consume 1qt per 4-6k miles before switching oil brand. I asked in an other post how to change the valve cover gasket and I received good response and thats what I'll do in about one month. I checked and clean the pcv and everything is top shape there. I'd really like to try some High Mileage Oil BUT my car requires synthetic 4718m gm specs. I cant find anything that is high mileage and 4718m specs. What would happen if I try a high mileage oil and change it every 3k miles that doesn't have the required specs? Or another oil weights that is not gm specs or recommended weights? I did a compression test and everything is top shape (wet and dry tests). I'm asking...
 
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Messages
1,513
Location
Peterborough
You wont hurt anything doing that, it that oil will pour well when its cold. BUT, Id do what the others have stated. Go for a regular 10w30 HM oil. If its still consuming LOTS, maybe go up to a 10w40 if your in a warm climate or 0/5w40 syn.
 
Messages
4,622
Location
Western Washington
On a four year old car with 106k miles on it, why are you still worried about the GM specs for the oil? Is warranty still an issue? Besides, many oils would meet that spec if they bothered to get certified. IIRC, that spec was designed to limit sludge/deposit control in some of their cars that didn't have an oil cooler. Point is, I wouldn't limit myself to just the oils on that spec list. I'd find a good oil that limited my leakage and use that with a reasonable OCI. Just did a quick search and found this thread for you... http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1131749&fpart=1
 
Messages
8,859
Location
Texas
 Originally Posted By: Spykem4e
If my car calls for a 5w30 weight oil and I put a 0w40 in it, let say to reduce oil consumption, what's happening inside my engine? -Mark.
I've posted this before, but I personally do NOT believe that heavier oil always results in lower oil consumption, sometimes it increases consumption. Thicker oils will leak past gaskets and seals a little slower. They will drip past valve guides a little slower. But IMO (and I've got a little personal anecdotal experience to back it up) thicker oils may actually result in HIGHER oil consumption past worn rings. This is because oil doesn't "get past" the rings at all- it gets sprayed on the cylinder wall while the piston is up, and then the rings have to scrape the oil back off the walls. Weak/worn rings don't scrape as well, and thicker oil is harder to scrape, so more thick oil gets left on the cylinder walls and burned than the same engine with thinner oil. Analogy: spray water on your windshield, and the wipers can scrape it off in one stroke. Now put maple syrup on your windshield and see if the wipers can clear it off as easily.
 

PT1

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5,746
Location
near the mistake
 Originally Posted By: 440Magnum
Analogy: spray water on your windshield, and the wipers can scrape it off in one stroke. Now put maple syrup on your windshield and see if the wipers can clear it off as easily.
Then spray maple syrup on 1/2 of your windshield and coat the other 1/2 with hot roofing tar...then turn on your wipers and shazaam! You will now understand how piston rings work.
 
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