Car has run on the wrong grade of oil for 20 years

[FCD]

So my 1975 Capri has run on various brands of 10w40 synthetic blend and some dino / mineral oils since about 1995 until last August/September, the reccomended oil for it was 20w40 or 20w50 , can it have harmed the engine in any way? the manual does say it can be run on 10w40 in very cold climates but it reccomends not to drive too agressively while running this oil , i live in southern Spain where the lowest temps would be around 0 to -5c ( high 20s / low 30s for you americans) the oil pressure is good since i switched to 20w50 and is as expected higher, a compression test showed all of the cylinders to be within spec, the reason i ran a 10w40 is because a guy at the Ford dealer reccomended it to me and at that time i thought oil was oil and that there wasn't much else to it.
The valve train on my engine does sound a bit louder than average but not worrying and it hasn't changed much over the years although 20w50 does seem to have quietened it down a bit

 

[donnyj08]

10w40 is plenty thick. you didn't hurt a thing by running it. It is still running afterall!

 

[Bud]

You are worrying needlessly. Obviously whatever has been run in the car is working. Go have a beer and relax.

 

[Ihatetochangeoil]

^^ What he said. Maybe....While you're relaxing, have an enjoyable? read about viscosity and oil pressure and manufacturer's recommendations:

http://www.bobistheoilguy.com/motor-oil-105/

 

[HTSS_TR]

Originally Posted By: FordCapriDriver
So my 1975 Capri has run on various brands of 10w40 synthetic blend and some dino / mineral oils since about 1995 until last August/September, the recommended oil for it was 20w40 or 20w50[/b] , can it have harmed the engine in any way? the manual does say it can be run on 10w40 in very cold climates but it recommends not to drive too aggressively while running this oil , i live in southern Spain where the lowest temps would be around 0 to -5c ( high 20s / low 30s for you Americans) the oil pressure is good since i switched to 20w50 and is as expected higher, a compression test showed all of the cylinders to be within spec, the reason i ran a 10w40 is because a guy at the Ford dealer recommended it to me and at that time i thought oil was oil and that there wasn't much else to it.
The valve train on my engine does sound a bit louder than average but not worrying and it hasn't changed much over the years although 20w50 does seem to have quietened it down a bit

Synthetic 10W40 and conventional 20W40 are similar in thickness at operating temperature, the advantage of synthetic 10W40 is it's thinner than dino 20W40 at start up(both are still too thick at any start up temperature).

I think we don't have 20W40 in US for many many years. Just use 10W40 and don't worry about it.

 

[Yah-Tah-Hey]

The lifters are probably leaking down somewhat and not achieving zero valve lash which equals noisy.

 

[Olas]

If its been in use for the last two decades and you still drive it today I don't think it's fair to say you used the 'wrong oil' - maybe not optimum but surely not wrong..

 

[DBMaster]

My 1989 Honda Accord's recommended oil was 5W-30. Back then, I would have been part of the thicker is better crowd and I didn't know much about oil. I used 10W-30 synthetic until the last few years I had the car and then switched to Rotella synthetic 5W-40. I did 10,000 mile oil changes. The car had 353,000 miles on it and was running fine in 2012 when I got rid of it (wrecked it).

So, I would not give this a second thought.

 

[FCD]

I knew that it probably hadn't hurt anything but i just wanted to hear what you "experts" thought , i changed it for a 20/50 because sometimes in summer i noticed the oil pressure got a bit too low ( just above the red line) now it's great at all temps

 

[Jetronic]

the reason 10w40 was not recommended, was because of poor quality viscosity improvers back then. 10w40 was likely to shear down to a thin 30w oil or worse.

This is less of an issue these days.

 

[FCD]

The reccomended oil is a 20w40 or 50 , but i haven't ever seen 20w40 anywhere or anyone that uses it , everyone i've asked runs 20w50 in these engines specially in a hot climate like where i live

 

[FCD]

True because of that 10w40 used to get a really bad rep

 

[abycat]

Originally Posted By: HosteenJorje
The lifters are probably leaking down somewhat and not achieving zero valve lash which equals noisy.


I havnt checked but his car might have non hydraulic lifters so maybe a lash adjustment might be needed. But for the oil reccomendation I think a 5w40 diesel oil would work great.

 

[Shannow]

Originally Posted By: Ihatetochangeoil
^^ What he said. Maybe....While you're relaxing, have an enjoyable? read about viscosity and oil pressure and manufacturer's recommendations:

http://www.bobistheoilguy.com/motor-oil-105/


My advice to the OP is to NOT read that...

Quote:
Since the oil with a viscosity of 10 cS at 212°F thins to a viscosity of 3 cS at 302°F we will get more flow.


In the former he is referring to KV100, which IS measured in Cst (not cS), in the latter he is referring to HTHS, which is measured in Cp (and not Cst, and certainly not cS, whatever they happen to be).

The HTHS is what protects in areas like bearings an piston skirts, and is the behaviour of the oil under these high shear regimes.

Has NOTHING to do with "flow" under these high shear regimes.

Quote:
The higher flow works harder to separate the engine parts that are under very high stress.


Utter rubbish...

Quote:
Then use the oil viscosity that gives you 10 PSI per 1,000 RPM under those circumstances. For some reason very few people are able to get this simple principal correct. I cannot explain further.


He can't explain further as it is drivel, and has no founding in scientific basis. He's taken the racers rule of thumb for small blocks, and (mis)applied it across the board to everything.

Quote:
You should use whatever it takes to get 75 PSI at 6,000 RPM during the lifetime of the engine. This formula works in all situations.


Have read MANY MANY SAE papers, and never come across this...

the end bit about "rate of heat generation" is waffle.

Yeah, he's got a Maranello (did you pick that obscure detail up ?), and he runs 0W20 in it.

At least his medical advice articles carry a disclaimer that it's only an opinion piece.

 

[Shannow]

Originally Posted By: Jetronic
the reason 10w40 was not recommended, was because of poor quality viscosity improvers back then. 10w40 was likely to shear down to a thin 30w oil or worse.

This is less of an issue these days.


Yes, I agree.

It's still my least favourite grade, largely because of how poorly it performed in the early days (FFS, it only had to have the HTHS of a 30 grade), and the poor performance of the VIIs at that level of treat rate.

It's still a poor grade IMO.

If I want stout, it's 15W40, otherwise it's 5W, and 0W synthetics.

 

[Torrid]

Originally Posted By: Shannow
Originally Posted By: Jetronic
the reason 10w40 was not recommended, was because of poor quality viscosity improvers back then. 10w40 was likely to shear down to a thin 30w oil or worse.

This is less of an issue these days.


Yes, I agree.

It's still my least favourite grade, largely because of how poorly it performed in the early days (FFS, it only had to have the HTHS of a 30 grade), and the poor performance of the VIIs at that level of treat rate.

It's still a poor grade IMO.

If I want stout, it's 15W40, otherwise it's 5W, and 0W synthetics.


I'd agree with this, I've always liked 15w40 as an economical choice for performance applications. I'd say this would be a good option for LSX and earlier GM V8s and 4.3 V6s. I also like 10w30 conventional for this purpose and is what I'll be doing in my two cars since they don't require synthetic and I don't put a heavy amount of miles on the cars. If they were higher performance driven vehicles I'd consider 15w40. I always ran synthetic in my GTO but these days I'd pick the 15w40 of I still had the car.

 

[crazyoildude]

in 1989 Honda built great long lasting engines...

 

[B320i]

I don't think there's an issue, and the recommendations back then were related to the VII's poor performance as it has been said here - this is related to the temperature in which the engine would run.
You wouldn't run the 10w40 into warmer conditions because it would break down too easily.

An oil that would be on-par, but probably much better would be a 10w50, which (at least in Australia) can be had in fully-synthetic options.
Although, as Shannow pointed out recently, your cold-starting viscosity doesn't matter a whole lot until the very extremes of each grade, and, if I read correctly, a thicker grade may even be better at startup.

 

[Garak]

Yep, just running on borrowed time, by the looks of it.

 

[Diego3336]

I've used 15W40 and even 20W50 instead of the right 5W30 for my engine for at least 10 years, thanks to Ford and their wrong-printed manuals too, but it was in a Escort with the 1.8 16v engine instead of a Capri.

Now I am using Valvoline MaxLife 5W30, but despite a little less noise from the lifters, I don't feel too much difference compared to the 15W40 DuraBlend I was using before, to be honest.