Can a thicker oil ever result in increased oil consumption or damage an engine?

Messages
2,480
Read some posts below where it was said that a 15-50 caused an increase in consumption. Can this actually be true? How? What about the post that said "years back, I killed my Corolla by using 20-50. How?
 
Messages
8,937
Location
SC
quote:
Originally posted by Dr. T: What about the post that said "years back, I killed my Corolla by using 20-50. How?
I can think of one scenario: It's 25 degrees F below zero, he cranked the car (a miracle in itself with this weight oil) and immediately took off, redlining it in every gear. [Wink]
 
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47,824
Location
Everson WA - Pacific NW USA
I doubt increased consumption. But here's a scenario to go along with the ealier petroleum 20W-50's not pumping at cold temps. Most of the early viscosity improvers and pour point agents were not exactly stable. So in a nutshell it was a nasty cycle. When the oil gets hot the pour point agents (solvents) evaporate off - so the oil thickens with age - then when you need those thining agents (cold weather) the oil is even thicker so more wear....and some of these API 20W-50 oils even got so bad they indeed would turn into black tar of death - and I'm talking less than 3000 miles. Maybe not all the wear would happen in one oil change interval - but it could get you in less than 80,000 miles. Not so amazing about the guy and his Corolla - it happened to my Datsun 510 when I was a youth. And I thought I changed my oil regularly. The companies, Castrol in particular hyped these oils for the hi reving 4's - AND the logic amongst us stupid boys: The thicker the better!!!
 
Messages
901
Location
Northern Illinois
Depends on what you call "use" but a thicker oil will definitely cause any leakage at the crank seals to increase because of higher pressure. I have also noticed worn guide seals leaking worse. I theorized it was because the thinner oil drains off the stems fast and the leak can only accept so much while the thicker moves down the stems slower and more of it gets past the seals.
 
Messages
238
Location
Monterey Park, CA
I agree if you oil get so thick it doesn't flow well anymore, then it's going to cook when it gets in the valve covers by staying in there too long and will gum and varnish up. I have seen this with guys who put in too much STP oil treatment. It turned their oil into molassas. It got into the cylinders too. The valves were caked with carbon, and there was a ridge of carbon in the cylinder bores. That's why the engine was pinging like crazy.
 
Messages
43,676
Location
'Stralia
Was doing some thinking today regarding thicker oils. Back when they were first released downunder, there was a lot of hype about the new "Made for Australia" oils that were ridiculously thick (35W-70 was a common one). Even the big oil companies make a 25W-60 for older cars. With the thick oils, the oil pressure was almost dead constant. Which to me indicates that it is on the relief valve all the time. This should lead to hotter average oil temperatures, and possibly more volatilisation and sludging.
 
Messages
485
Location
Montgomery, AL
quote:
Originally posted by Pablo: Most of the early viscosity improvers and pour point agents were not exactly stable. So in a nutshell it was a nasty cycle. When the oil gets hot the pour point agents (solvents) evaporate off - so the oil thickens with age - then when you need those thining agents (cold weather) the oil is even thicker so more wear....and some of these API 20W-50 oils even got so bad they indeed would turn into black tar of death -
Very good point to think about when stories about the older oils are told. I'm glad modern pour point depressants are often PAO.
 
Messages
903
Location
CA
quote:
Originally posted by sprintman: 20W50 still the biggest seller in Oz but X/40W probably will take over soon. Hey I even went to a 10W30 Pennzoil for Auto-Rx cleaning, was pretty apprehensive when I poured it in!
Hey, even I have relaxed a bit on viscosity. I changed the oil in by wife's truck last week from M1 15w50 to Redline 10w40. [Razz] I plan on doing the same on my crusty '88 civic. I hope switching to an ester based oil after running a PAO oil after 200k isn't a problem. [Roll Eyes] Now I need to convert an old Suzuki to Redline and M1 is out the door. Too bad really, I sure liked the MX4T. IMO it is the best Mobil oil product.
 
Messages
5,785
Location
Dixie
Dr T, Engines will run hotter with heavier oils, so if you had a small, high revving Honda motor that called for 5w-20 and ran 20w-50 in it, you could overhead the engine in the summertime. Oil pressure would also be through the roof, and the oil pressure relief valve would be "shunting" some of the oil pump output back to the pan all of the time. In an older German engine like yours, that specs 15w-50 or 20w-50 for temps over -10C/14F, there would be no problem. The bearing clearances in these German engines are designed so they can use the thicker oils and the oil pump and oil filters are also designed with high viscosity oils in mind. My Audi has the same viscosity recommendations as your BMW engine. As an experiment I am running the Amsoil 20w-50 synthetic in my high mileage, 209k, 2.3L Audi engine this winter - I'd normally run 0w-30 or 10w-30 synthetics. So far the only thing I've noticed is that fuel efficiency has dropped by 5% and the oil pressure stays pegged @ 5 bar all the time! Tooslick
 
Messages
453
Location
Galveston, TX
quote:
Originally posted by Shannow: Was doing some thinking today regarding thicker oils. Back when they were first released downunder, there was a lot of hype about the new "Made for Australia" oils that were ridiculously thick (35W-70 was a common one). Even the big oil companies make a 25W-60 for older cars.
Shannow, no need to recall until "back when..." Right now, today, Australian Market versions of most cars, have manuals that specify the use of motor oils heavy enough to make Americans freak out. I think they start out at 10W-40, with instructions to use 20W-50 not uncommon. And these are the same engines many people claim are "made for 0W-20, 5W-20 oils." Could it be because it is a Las Vegas desert type environment Down Under? When I was in Vegas last month, I noticed that 10W-40 was very prominent on the shelves, and 5W-30 nowhere to be seen. In NY, you have to look hard to find the 10W-40, if you even find any at all. I'm talking mineral oil. Didn't bother to look at the syn's.
 
Messages
43,676
Location
'Stralia
Flimflam, I was working at a Shell service station back in 1987, and we had Shell Super SF 20W-40, and Shell XMO 15-30. Customers would routinely question even the 20W-40 as being to thin for Aussie conditions. The XMO was credited as having wrecked nearly every engine it was ever run in. Only other products on any of the shelves anywhere was 20W-50, and people liked it. Castrol and AGIP had 10W-50s, which were considered to be magic oils, capable of anything. I'd run 20W-50 with STP, and then start it in -5 degree (celsius) mornings (tappet rattle anyone ??), drive it to the snowy mountains in winter, and then drive through the outback in summer with it. Never seemed to have a problem, but now I hate waiting for the gauge to show pressure.
 
Messages
453
Location
Galveston, TX
Shannow, why'd ya think that XMO 15W-30 wrecked engines? Because it was too thin? I have never encountered Shell XMO 15W-30, but I see a lot of people moan and groan about Shell....the new Shell's, not XMO 15W-30. Anyway, for Australian conditions, 20W-50 is great stuff. I have never been there, but I know it is hot. All this talk about all the wear and tear happening on start up, of having to use 0W-10 "easy-flow" oil, I really dunno! I had a 351 cube-inch V-8 (5.8 liter to you!) Ford, it was kept and driven in New York for 4 years, all it ever had in it was Castrol HD-30. Occasionally, In a Heat Wave Summer, I'd use HD-40. In the coldest NY winters, I never had a problem with that oil that all my "with it" friends tell me, is too thick. In fact, even Ford service hand-out flyers tell me it is too thick, haha! It had more than 150,000 miles on the clock the day I sold it off. I never had the valve covers or whatever you call the thingamajig that covers the top of the engine, off. When I handed the keys over to the new owner, that old 351 V-8 [Confused] sounded exactly the same as the day I first got it. Without the benefit of the newfangled snake oils with their "excellent wear characteristics."
 

Patman

Staff member
Messages
22,012
Location
Guelph, Ontario
I still think 50wt oil is too thick for best engine protection, even in very hot weather. I'd like to see some of you guys who run in hot weather try out doing oil analysis with a 15w50 or 20w50, and then with a 15w40 (or 10w40/5w40) I bet with most engines out there the 50wt oil would show higher wear numbers. Most engines are not designed with this thick of an oil in mind, the clearances are simply not that loose.
 
Messages
1,527
Location
Southeast United States
I don't think climate has much to do with the operating temps of engines. That's assuming the cooling system is working normally. Once an engine warms up to it's normal temp, even 30-40 degrees of ambient temperature isn't going to increase the combustion temps that much, if any. Also, if the thermostat still controls the engine coolant at 180-190 degrees, and an oil cooler keeps the oil temps below 180 degrees, an engine should run the same in 100 degree weather as 30 degree weather. Granted, all cooling systems have to be working normally. But wouldn't it be better to add larger radiators and oil coolers than run thicker oil?
 
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49
Location
MS.
When I bought my Toyota Camry, in Jan 2000, 4 not a 6. The dealer told me to put 10W30, into it. I asked him if he ever read the manual, for it says 5W30, and the oil cap says the same. I live in MS, and he told me, that it was for cold places not down here. Of course the car company is saying for all places, but he said he didn't even know where one could buy 5W30, so I told him WalMart, for I use it in another car. My grandfather ran 10W oil all the time in his cars in Ohio, and got over 100,000 out of them, in the 40's back when you had to over haul a car around 70,000, but he never had to. They were still in good shape even over 100,000. So I think thin is probably better.
 

MolaKule

Staff member
Messages
21,950
Location
Iowegia - USA
LoneRanger, "Granted, all cooling systems have to be working normally. But wouldn't it be better to add larger radiators and oil coolers than run thicker oil? " I couldn't agree more. Problem is, making vehicles more aerodynamic also reduces front end area, reducing size of radiator. Hey, I think the Aussies are great people, but could it be that those really thick oils is more a state of mind or oil company advertising than mechanical clearances or other necessities? I mean, these same engines are being used in both countries with little modifications between the two, while the EPA forces thinner oils on us, the Aussies get thick oils. I see two extremes here with the same engines. I guess the same thing could be said about the Europeans.
 
Messages
917
Location
Singapore
quote:
Originally posted by pruntyc: When I bought my Toyota Camry, in Jan 2000, 4 not a 6. The dealer told me to put 10W30, into it. I asked him if he ever read the manual, for it says 5W30, and the oil cap says the same. I live in MS, and he told me, that it was for cold places not down here. Of course the car company is saying for all places, but he said he didn't even know where one could buy 5W30, so I told him WalMart, for I use it in another car. My grandfather ran 10W oil all the time in his cars in Ohio, and got over 100,000 out of them, in the 40's back when you had to over haul a car around 70,000, but he never had to. They were still in good shape even over 100,000. So I think thin is probably better.
I have the same car as you. 50wt seems to be good for this engine. http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=000168 Cant get anything less than a 40wt here in hot tropical Singapore.
 
Messages
152
Location
Ventura, CA
pruntyc, every Toyota dealer carries genuine Toyota 5W-30 motor oil (or can order it). Discount dealers charge only $1.39 per quart for it and some will ship it to you by the case (12 quarts for $16.00) The 10% UPS charge is offset by not having to pay 8% sales tax. To find discount dealers go to www.yahoo.com and use Toyota Discount Dealers as your search words.
 
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