The quote below is from a guy in Denver Co. who runs the hell out of a 34 Ford Roadster with a "Built" Flatmotor. He has put over 100,000 miles on the car since 1996. He also changes the oil every 3000 miles.
"30wt Valvoline in the winter and 40wt Valvoline in the summer.... the same recommendations 'Ol Henry made"

 

I've used Quaker State since I was little. My father used Quaker State. Living in CA where its hot, I use 10w 40w. The key is like everyone says. Change the oil when it needs it. Here's a tip...... I have been using Wal Marts brand oil and their filters. I found out from an distributor that the oil is manufactured by Quaker State for Wal Mart. Costs less same oil. The filters..... Fram makes them for Wal Mart. You didn't hear it from me though LOL..... I heard Pennzoil gums up the engine if you wait to long on oil changes.

 

You should use the viscosity originally specifed by the manufacturer. Bearing clearances, etc. were designed specifically to include the oil (viscosity) specified. Using multi-viscosity oils where heavier single viscosity lubricants were intended does not provide the lubrication, heat displacement, etc. that the design intended. Viscosity is critical to the original design intent. Unless you are willing to alter the clearances and lubrication supply (oil pump, oil passages, etc.), don't try to second guess the original design engineer. Today's oils are much better than yesteryears, however, viscosity ratings are still viscosity ratings.

 

Very good point. Only problem being the manufacturers may change their recommendations retro-actively without your knowledge. I remember back in the late 80s reading GM professional technical bulletins that retro-actively pulled their recommendations to run anything heavier than 10w-30 in their older SBCs. Studies had shown longevity was suffering. The advice came a little late as 90% of the engines in question were probably out of service.

 

That's the point. Service recommendations may change, however, the original design recommendations remain constant. The older engines were designed for 30 weight oil and should use 30 weight oil as lighter oil can reduce useful life. Later engines were designed for multi-viscosity oil and the use of heavier oils may be just as detremental.

 

I'm sure viscosity has some issue and merit here. I've seen people using various viscosity oils and they get 300,000 + miles on their engines. I've also seen people get 50,000 miles on an engine. I think its not so much the oil, or the viscosity of the oil as it is changing the oil regularly and making sure you oil level is correct.

 

Maintenance has a lot to do with longevity also, however, being an automotive engineer, I have some experience in designing bearings/clearances and the considerations that are given for viscosity. All I can do is give my input based on experience. Those that choose to not follow the OEM recommendations, are playing by their own rules and should be prepared to pay later. I'm not saying that problems will definitly occur, just that they are increasing the likelyhood.

 

Alright, I'll bite. Are you saying that 30w oil and 10-30w oil are not the same viscosity once the engine has reached its normal operating temperature? It is my understanding that they are the same. The only difeerence should be that the 10-30 does a better job of lubrication at temperatures below the normal operating temp. Is this incorrect? I'm always willing to learn from those in the know. John

 

Me too John. Your understanding is the same as mine. But I am confused by it all. A quart of 10W-30 conventional and a quart of 10W-30 synthetic should have similar viscocity at -20 degrees. That is far from the case. Hopefully someone will explain it to me here.

 

I was told by a very reliable source (employee of oil manufacturers) that the reason behind the multi-grade oil was exactly as you guys explained. A 10-30w oil is designed so that on cold mornings etc. the 10w thins the oil to lubricate under cold conditions. Once the engine has reached "normal" operating temp, the oil thickens to the 30W. as does 10-40W and 20-50W. Thus they recommend various viscocities according to your temperature and climate. A person in Arizona most likely will not need the 10W whereas the 40 and 50W may be a consideration. Now, I do know that Ford recommends a 5W - 30W on my 98 F150? That oil is like water. I also know that oil change places usually put 10-30W versus the 5W.... Don't know about the synthetic oils or how they work.

 

You are partially correct. SAE 30 and 10W30 are both the same viscosity after reaching higher temps. However, 10W30 is a 10 weight oil at lower temps. This DOES NOT mean that it lubricates better at lower temps. The bearing clearances on the older engines were designed for SAE 30. Clearances are engineered to maintain specific oil film thickness within the joint. Using lighter oil than designed is the equilvalent of running with worn bearing. The lighter oil would not provide the designed oil film thickness that was intended since it would flow much easier through the joint. Think about it. You want oil to be between your bearing and the mating surface.

Confusing, isn't it? Think of it as trying to carry water in a leaky bucket to put out a fire. You can carry the water in a leaky bucket, however, if the holes are too big, you won't have as much water left in the bucket for the fire. Here's a link that might help to understand oil viscosity.

http://www.valvoline.com/carcare/art...=ccr20040601ov

 

Ok, I went to the website provided and I read about viscosities. It does a good job of explaining the different ratings. And I acknowledge that it points out that owners should follow the recommendations of the manufacturer. I even can see the logic behind the bucket metaphor. However, I am suspicious that the multi-viscosity oils may have been recommended by the manufacturers if they would have existed when my vehicle(s) was manufactured. I can invision the oil flowing into my main bearings as both the 30 and the 10W-30. It would seem that if the 10W-30 is thinner and thus flowing out of the bearing quicker, then the flow of oil from the oil pump would more easily flow in to replace it. It also occurs to me that the cold "thicker" 30 would not flow through the journals very well until it is "thinned" by the heat of the engine. So I guess I am not convinced that I should not use multi-grade, and won't be until I see an oil supplier tell me otherwise. Sorry this is so long, John

 

I've read the link and am good with what Dodge says for the most part. I understand a looser clearanced engine would appreciate a thicker oil to provide some cushion. Until that -20 morning in Iowa when the straight 30W is laying in the oil pan because it is thick as molasses and the engine is knocking like hell for 10 seconds. A perfectly good engine will do this here, and it can't be good. A multiviscocity will pump faster. Way faster if it is synthetic.

Be patient with us Dodge. I'm a novice at oil specs and willing to listen to reason. But I am pretty sure my engine banging on startup in extreme cold can't be a good thing. Straight 30W is literally like tar in the winter.

And my wife's Escape takes 5W-20. Talk about water. But I am told her cam won't get any oil if I go heavier. So I listen to Ford and run it anyhow, though it seems like a coporate gas mileage trick fleet rating trick. Only mention that because I usually trust the engineers even when I question it.

 

My personel perference is Castrol Heavy Duty 30.

Michelle

 

Every serious flatmotor builder that I am aware of uses a multi grade oil. Dinosaur or synthetic is more a personal choice in a fresh engine but I would never suggest synthetic in an old engine. It is asking for leaks to show themselves.
Neither would I ever think of using a single grade oil in anything except as initial break-in oil that will be changed twice in the first 500 miles. The single grades do not have the additive packages that reduces wear, this also includes racing oils. Never use racing oil in a regular driver.

Viscosity is an over used term. Think slippery today. A premium multi such as Castrol 20W50 is a much slipperier oil than any 30W thanks to the additives and is the only oil I use in any of my rebuilds.
BTW, my comment above about break-in is a 2 parter. Change after 20 miles or so and check for metal particles. The remaining 480 miles is to seat the rings; something almost impossible to do with a very slippery multi.

For a well worn engine try Shell Rotella or any other multi designed for heavy truck service; these are usually a 10W40. You need to look for the CH/CI/CJ API code or whatever is current today. I parked my 318 Dodge van last month at 382K, bent a pushrod by forgetting to upshift coming out of the toll booth (had a very heavy load and I prefer to shift maually then). At about 65 in 2nd I heard a funny noise
My replacement is a 79 Ford E350 12' cube van; just finished putting in a nice 351W.

Up here in NH Ive never had a start-up bearing rattle with Castrol, even at -35F. Flathead, Y block, BBC or modern drivers.

BTW my 94 Taurus manual says to use 5W30, I use 20W50 and after 182K it is down maybe a pint at 3K change intervals. This car gets driven fast, typical cruising speed on the Interstates is 80-85.
Second guessing the OEM IS A GOOD THING since they have more than the consumer in mind. In order to meet federal MPG regs they use the lighter oils to reduce friction. I'd be willing to guess that there arent too many hi miler Taureses on the road that use the OEM spec. Even worse are some of those new vehicles that specify 0W20!!