Using "thicker" oil

Messages
31
Location
SF Bay Area
This is a question for me for a long time and I think you guys can help me with that. Let say, a car's factory recommend(modern Honda and Ford) 5w-20(I am in Calif so no sub zero temp), what happens if I use a 20W-50 oil in it? It is not a turbo engine. But will "thicker" oil give better protection? Or will it hurt the internal parts because it is thicker? Will it cause more pressure on the interanl parts? I know the mileage may hurt but it is immaterial to me if it gives better protection.
 
Messages
100
Location
Shelton, WA
quote:
Originally posted by bigjason: ... But will "thicker" oil give better protection? Or will it hurt the internal parts because it is thicker? Will it cause more pressure on the interanl parts? I know the mileage may hurt but it is immaterial to me if it gives better protection.
I have run Mobil 1 0W-40, GC 0w-30 and Motorcraft 3W-20. The Motor craft was the first 2 changes. The analysis of M1 and GC showed good results with the GC haveing a slight edge. Mileage improved with the GC by about 1.5-2.0 MPG. I used a 5k mile chamge interval. No I am reverting to Motorcraft 5W-20 to compare results. Thus far, Motorcraft seems to match the GC in MPG, but really need more samples to be certain. So far at 900+ miles, I notice no perceptible difference in sound or performance. The oil appears as clean as when it was put in. About the only difference I can discern is that the engine does seem to require fwer cranks to start in the am. But thats only a perception. If the oil stands up as I think it will, I'll probably continue to use Motorcraft on a 3k change cycle. P.S. My drive characteristics are 95% Hiway. 2200 RPM I'd estimate with passing reaching 6000 RPM at most. - Bob
 
I put 10w40 in my Silverado 5.7L rather than the usual 10w30 (same brand & type) and noticed two things: Oil pressure ran about 5 lbs higher and coolant temperature ran about 20F higher under heavy load. Neither of which was good. It seems oil pumps and galleys are designed for a specific weight of oil and using a heavier oil than the engine was designed for restrict oil flow. Also, a ligher oil cools better than a heavier one. From reading numerious posts on this board I've gathered that the lighter the oil the better - and here's the catch - as long as it provides adequate lubrication.
 
Messages
13,132
Location
By Detroit
quote:
Originally posted by williar: I put 10w40 in my Silverado 5.7L rather than the usual 10w30 (same brand & type) and noticed two things: Oil pressure ran about 5 lbs higher and coolant temperature ran about 20F higher under heavy load. Neither of which was good.
Interesting. What is your normal oil pressure? An extra 5 psi may not be all that bad, though. At least in my case I think the move to 10w40 was good (though I don't have a temp gauge). I was getting 35 psi with 5w30. 10w40 gives me 44 psi. Spec for my engine is 40-60 psi. But that does not mean the 35 was bad and maybe I should be running 10w30. [I dont know] EDIT: Williar, what brand/type oil are you using? EDIT2: Why did I think you were talking about oil temp. You said coolant temp. Well I have the factory gauge and it does not read any higher with 10w40, but how do you read a gauge that has no numbers, just "NORMAL." It usually always is on the OR part when warmed up. I will say the pressure would drop about twice as much (about 4 - 5 psi)under hard driving with the 5w30 (it was Vavloline Durablend and Maxlife 5w30s) than it does with the 10w40 Maxlife and 15w40 Durablend (currently running). [ August 05, 2004, 04:17 PM: Message edited by: TallPaul ]
 
Messages
562
Location
Austin, TX
We have one car running 15w-40 with no change in performance, mileage, etc. vs -30 weight. The other with 5w-40 is smoother but you feel the drag a bit more than with 10w-30 and I *think* (it a little early to be conclusive) the mileage has dropped 1-2 mpg. So the answer is it depends on the car and how its used. Some European cars require -40 weight. Basically almost anything can run and survive a long, long time on 10w-30. I don't think there is much payoff running 5w-20 in terms of being on the leading edge. I am waiting till lots of high mileage examples are out there. The downside to high spread oil like 10w-40 is that the chemicals used to allow the range can break down leaving residue and a thin, out of grade oil. This is less of a problem now than a few years ago and generally not an issue with synthetics. Thick oils, like 20w-50 are usually safe, but require longer to reach the engine components at start up as it flows slower. Most agree start up is where the wear occurs. Some engines might not be designed for thicker oils in terms of oil pumps and clearances.
 

pmt

Messages
148
Location
MN
quote:
Originally posted by williar: "I put 10w40 in my Silverado 5.7L rather than the usual 10w30 (same brand & type) and noticed two things: Oil pressure ran about 5 lbs higher and coolant temperature ran about 20F higher under heavy load. Neither of which was good." I had somewhat similar results using Rotella Synth 5W-40 in my 2003 GMC 4.3L, compared to various 5W-30 and 10W-30 oils previously used. Gained about 5 psi oil pressure, but coolant temperature showed no increase under any load condition. "From reading numerious posts on this board I've gathered that the lighter the oil the better - and here's the catch - as long as it provides adequate lubrication." I totally agree with this statement, but would add one additional qualifier - and as long as oil consumption is reasonable.
 
Messages
7,409
Location
Austin, TX
quote:
Originally posted by williar: ...the lighter the oil the better - and here's the catch - as long as it provides adequate lubrication.
My sentiments exactly.
 
Messages
1,381
Location
Southeast Kentucky
Jason, you ask a good question. The industry's gradual switch to thinner oils flies in the face of many long standing opinions and beliefs that 'thicker is better'. Many folks, myself included, felt that 5w20 was designed only to get a motor to achieve CAFE results and that the engine wouldn't last 100K miles. Used oil analysis have shot that theory full of holes. Many of these new 5w20's, especially Motorcraft, are tough synthetic blends that are giving excellent wear numbers. It seems that as long as the oil is stout enough to maintain a layer of lubrication bewteen parts, thinner is good. I wouldn't recommend it for every motor, but for those spec'd for 5w20 I don't think a thicker oil is the answer.
 
Top