I may be crazy (there are those who think so sometimes). But everyone using these 5W20 and 5W30 etc.... Now in the winter, it might be OK. But in the summer, it just seems to me like that is crazy. When it is 110 degrees out side, don't we need something a little better??? It just seems to me that that thin oil is not going to hold up as good as something thicker.

OK. Let the bashing begin!!!

 

You're not crazy. Supposedly, 5w30 and 10w30 will have the same viscosity when hot. But since 5w30 starts out with a 5 weight oil instead of a 10 weight, I think it does wind up being a little thinner.

I just run 10w30 year round. It seems to work well.

 

5w30 is just fine all year round. Our engines are liquid cooled so they have the ability to maintain fairly consistent temperatures all year. I highly doubt the 10 degree difference in coolant temperature in the summer (say maybe 205F) would account for a significant increase in oil temperature and cause the oil to break down at a significantly higher rate than when it’s running at 195F.

 

If you look at a lot of used oil analyses on Group II dino oils you will find that the 30 weight multis shear back to a 20 weight real quick. With the oil companys now able to produce a very shear stable, quality 20 weight Group III synth blend (see the Motorcraft 5w20 UOA), the car mfgrs just can't resist spec'ing it in order to raise their CAFE numbers. An added benefit of a shear stable 20 is that there are not a lot of shreaded viscosity index improvers left around to sludge up the engine. All this combines to allow for good wear numbers, longer drain intervals and a clean engine.

 

Rusty, you're not alone in speculating that a 5W oil might be thinner at operating temperature than a 10W- , but that's not my experience. I use a 5W-40 synthetic and oil tests indicate that it measures exactly SAE 40 at 100c (212F), even after many thousands of miles of use.

I don't think that anyone has ever demonstrated an engine problem caused because of metal-to-metal contact because an oil is too thin. Many racers use a straight 10 or 15 weight oil when qualifying on a track to pick up a few extra horsepower. And those are high-performance, highly stressed and expensive engines.

The only practical reason I see for going with an oil over 30 weight is in high mileage, worn engines or engines with larger design clearances like diesels or some air cooled engines. Not a squeaky-tight modern engine like the Ford 4.6/5.4L.

If they leak oil, fix it, don't add STP!

Happy Holidays!

 

I understand another reason for the thinner oils is because the newer Ford overhead cam engines need to have the oil supplied quickly to the camshaft way up in the top of the head. Maybe so, but Ford had OHC four bangers for many years before the thinner oils were specified.

Now, speaking dino oils and pushrod engines, if you want to run a 5w30 in winter, fine, but why run it in the summer? A 10w30, since it starts with a thicker base oil, will have fewer viscosity index improver polymers and thus would be less subject to viscosity reduction from polymer sheer than would a 5w30. That's why you don't see either 5w30 or 10w40 heavy duty motor oils (I suspect diesel engines can really give motor oil a beating). My local Ford/Sterling dealer tells me the big trucks run 15w40, except in the winter they run 10w30.

Do viscosity index improver polymers sludge up an engine when they shear, or do they just improve the viscosity index to a lesser degree?

 

And the euros and Japanese have been selling OHC engines here for a long time, too. Maybe the new ones are built to tighter clearances?

I think we need to start being careful here. What you say may be true with conventional oils, but it may not apply to synthetics. I wouldn't thing twice about running a synthetic 5W-30 year round in a car or 5W-40 in a diesel. In fact, I do. The former in my '96 460 and the latter in the PSD.

In either case, we need to determine two things first:
Is the greater engine wear caused at startup when oil is thickest and flowing the least, or could it be under conditions of maximum heat and stress?
And even if an oil dropped to an SAE 25 from SAE 30 after VI additive breakdown, is that *really* a potential problem? (regardless of what the TV motor oil ads claim). Like I mentioned, a lot of racing cars with expensive, stressed out engines use much thinner oils than what we might ordinarily use.

We're all here to learn and do the best for our vehicles, it would be helpful to know the answers to these questions.

Mobil recently came out with a synthetic in 15W-50.
IMO, that's a completely ridiculous product with no practical benefits. Strictly a marketing scam for which they should be embarrassed. No one needs an SAE 50 engine oil, especially a synthetic. Just because they're making it, doesn't mean that a thicker oil offers any benefits. Unless you're leaking it or your engine is on the way out from wear. And I wouldn't waste my money on a synthetic in a worn out engine.
If someone likes gooey oil, STP or Motor Honey will do the same thing for a lot less money.

Andy Granatelli made an awful of of money over the years selling STP promoting the idea that a thicker oil was somehow better for an engine. Maybe it was true with the engines of 50 years ago, maybe it was never true, but the concept sure sticks in our minds, doesn't it?

Yes, absolutely correct. You might find it interesting that Ford has issued a TSB on the Powerstroke diesels suggesting switching to a 10W-30 from the previously-recommended 15W-40.

618400 - DRIVEABILITY IDLE - ROLLING IDLE
SPECIAL SERVICE MESSAGES
17268
1994-2003 MULTIPLE VEHICLES WITH 7.3L DIT - IDLE ROLL/LOPE ON COLD START
SOME 1994-2003 SUPER DUTY F-SERIES/E-SERIES AND 2000-2003 EXCURSIONS EQUIPPED WITH THE 7.3L DIT ENGINE MAY EXHIBIT AN IDLE ROLL/LOPE ON COLD START THAT LASTS UP TO ONE MINUTE. THIS CONDITION IS CONSIDERED A CHARACTERISTIC OF THE 7.3L. THE FOLLOWING STEPS CAN BE TAKEN BY THE CUSTOMER TO REDUCE THE LIKELIHOOD OF THIS CONDITION: CHANGE TO A 10W-30 OIL (XO-10W-30-QSD) LABELED CI-4 OR CH-4; PLUG IN THE BLOCK HEATER WHEN OUTSIDE TEMPERATURES ARE GOING TO BE BELOW 30F (-1C); LEAVE THE IGNITION IN THE RUN POSITION FOR A FULL 2 MINUTES SO THE GLOW PLUGS CAN FULLY HEAT THE CYLINDERS BEFORE CRANKING THE ENGINE.


That's another good question. I had heard that the VI improvers were nothing more than a type of plastic dissolved into the oil. But I can't see any engine getting sludged up using any reputable oil, synthetic or conventional unless it's been neglected.

 

5W30 has been specified as the oil for 90% of Fords and GMs in the past 15 years. With all this 5W30 being used we should have seen a reduction in engine life if it were significantly worse than 10W30 in regards to real world protection. We got the opposite Engines last longer than ever. Improvements in oil have allowed us to use thinner oils with the same or better protection.

 

Paarrothead: The idea of a synthetic oil that has no viscosity index improver polymers added, but still meets the grade requirements for a 5w30 is fascinating. Essentially the perfect motor oil. But there is the factor of price and we know engines will last at least as long as the rest of the vehicle on decent dino oil, so it may be overkill (unless in extreme cold or other extreme service). I might go synthetic, but would be reluctant to go the extended drain interval,possibly exacerbate existing minor leaks, and pay the price. I had been running a semi-synthetic though for several years. Now I am running a dino 10w40 that has a minor (10-20%) synthetic component. I cheat though as I have an oil pan heater for those cold SE Michigan mornings (rarely below zero F). That's right I am running 10w40, but anything less drops the oil pressure somewhat below spec, not that I could not go with a something-w-30, but I like the better oil pressure. This truck has 105,000 miles.

I think that longivity is not a concern with racing engines as they get frequent rebuilds.

 

5w30 for 160,000 miles in my 97 f150 4.6. No measureable oil consumption between 3000 mile changes, and blackstone oil analysis labs says engine wear is far better than normal. All oil changes with castrol or valvoline, and always a motorcraft filter. The following statement may be too simplistic for some to even consider, but I believe regular oil changes with a quality oil/quality filter are the primary key to long engine life. Throw the other issues such as 5w40 weight oil, syn oil, the amsoil hype, etc out the window. IMO. (however, i am in a year round warm climate (houston). i can see where really cold climates might require different maintenance/engine oil weight.

 

Paul, I don't want to trigger yet another synthetic vs. dino oil debate here!

You obviously know what you're doing and take good care of your truck with that straight-6.

I'm only trying to sort out and discuss the issures related to the original question, which was if a 5W-30 type of oil provided adequate all-season performance. I might have driven this off the track, and for that I apologize, but IMO the answer is yes. I wouldn't question the use of the recommended Motorcraft 5W-20 semi synthetic oil in a modern 4.6/5.4L V-8 engine or the 5W30s that are out there, which also seem to have a synthetic component.

IMO, using an oil rated at 5W-anything should provide very good strartup protection on a cold engine, where I believe most of the wear occurs. Jell-o offers no engine protection and bypasses right around oil filters until the engine warms up.

One of the most interesting products I have seen is the new Mobil 1 0W-40 synthetic. If it has minimal VI improvers added, it could be about the perfect motor oil. Everyone had to decide for themself if the price is worth it or if it offers tangible benefits. You know it's going to provide the hot oil pressure of a 40 while pumping fast and being all over the inside of an ice cold block in January. OTOH, I like my engine heaters, too.

 

I don't think that anyone went off subject at all. This is all very informative and I appreciate everyone's input. I have traditionally driven autos with a lot of miles on them and used heavier oil in them. I have to agree that in reality this debate is probably secondary to a good oil change schedule.

 

Well, the reason I went with dino 10w30 year round is that I did an experiment. My dad's chebby silverado 4.8L V8 had piston slap when cold with Mobil1 5w30. This happened mostly when the temperatures were below freezing. I could hear the knock from inside the house. It would do it mostly under load for about the first 1/8th mile down the road. From what I understand, this is a common problem with new GM engines.

I wondered if the oil could be too thin. So, I changed it and put in Mystik JT-8 10w30. This eliminated the piston slap completely. It runs nice and quiet now. I suspect that any non-energy conserving 10w30 oil would have given the same results.

I realize this is an unscientific experiment, and that this is only the results on one vehicle. However, my ears dont lie, and the noise is gone.

 

Yes, at least the older ones did. That is the main reason 10W-40 was disapproved for warranty a long time ago. "Black death" was the name given for that type of sludge.

Jim

 

Now our vehicles can be completely destroyed between "Michigan Body Cancer" and engine Black Death! It's only a matter of which gets you first!

BTW, would not a 5w30 be another Black Death oil in the earlier days? I think it has about as much VIIs as 10w40.