I want to switch to synthetic oil on my Volvo 240 DL 1990. I've called a few Volvo repair shops and they all seem to agree that it could cause the seals to leak. This one shop said it could miss up the rubber piston rings. But then on the Castol Oil web site they have a FAQ's list for synthetic oil called "Can You Handle the Truth about Synthetic Oil?" and it saids:

http://www.castrol.com/castrol/gener...tentId=7017050

"FACT or MYTH?
Synthetic motor oil will ruin the seals in older vehicles and cause leaks.
Answer: MYTH! We're not sure who leaked that rumor, but synthetic motor oil does not cause leaks. It is 100% compatible with all automotive seal and gasket materials. In fact, SYNTEC meets additional ACEA seal protection requirements not even addressed in API specs."

Which do I believe?

 

if you have used conv motor oil in the motor and it has alot of miles dont use syn oil (waste of money) syn oil is compatible you might get more life out of your motor syn oil is used from the start (new motor)

 

It's not about engine life. Synthetic oil's main benefit is extended drain intervals.
If you commute, you'll probably come up against time in service change intervals before mileage intervals, in which case synthetics are pointless.
As for synthetic oil causing old engines to leak, well, I've never had it happen.
Frankly, redblock engines benefit more from an older Service SE/F/G oil than a synthetic. All the modern oils have greatly reduced anti scuff additives, which is BAD for cam over shim engines.
There's a reason there are the "older engine" oil formulations on the shelves, and if you look at the viscosity ratings, it's not to reduce oil burning......
Castrol GTX is an excellent older engine oil, and pre Euro IV heavy duty diesel engine oils are also excellent.

Regards, Andrew.

 

Some synthetics will cause leaks that already exist, but are "plugged" with dirt and debris to begin leaking, as synthetic oils clean better. Older engine seals often have these microscopic cracks in them that get plugged. This is referred to as a "false seal." Synthetics sometimes clear those out, causing seepage... however, these types of leaks often will get smaller or even go away over time as the seal expands and mostly fills in that gap.

As for piston rings... they're made of metal, not rubber, and will NOT be harmed by synthetics. I have seen engines burn oil after being switched to a synthetic, but it's ALWAYS been because of failed valve stem seals- again, this is the whole "false seal" issue.

As for extended drain intervals, most synthetics not only increase the mileage interval, but the time interval, as well. They also will often improve fuel mileage slightly.

And the "older engine" oil formulations out there are simply normal oil with anti- leak/ burn additives. Basically, they've pre- added the "Restore" and "Stop leak." They all still meet current API standards, which means they have the reduced levels of zinc and sulfur- based anti- scuff additives- this is required by law. No one offers oils with the former levels of these additives, unless you've found someone with new- old stocks of SF rated oil. If you check the shelves, the only types of oil you'll find are oils with API ratings of SA/SB OR the current rating, which is SM. There's some amount of debate as to the effects of removing some of the anti- scuff additives on older engines, as there are other additives that mitigate things somewhat. Anyhow, because of this, my recommendation with regards to the "high mileage" oils is always as follows: only use them if your engine is actually burning or leaking oil. Otherwise, you're using oil that's been diluted and therefore rendered, at least somewhat- less effective as a lubricant. These oils came out in response to modern engines routinely lasting 150,000 miles or more. Guess what- modern engines last longer because they're better made. A modern engine with 150,000 miles has the wear of a 1960s engine with 75,000 miles. And the seals are better, too- Viton and silicone rubber compounds are far and away better than the nitrile and other compounds used way back when. I realize a '90 Volvo 240 probably doesn't have modern seals... but still, that engine isn't going to last longer because of "high mileage" oil, it's going to be because it was better designed and well maintained.

In the end, my opinion as a mechanic is as follows: Synthetic oils offer a lot of benefits to any engine. However, there ARE risks- small ones, but risks nonetheless- of an older engine leaking after you start using them, simply because synthetics clean things better. Also, high mileage oils really aren't worth the added price.

Take this as you will, as this is only my 2nd post in the RWD forum- I still haven't decided whether to switch my 740 to synthetic oil or not yet. I use synthetic in everything else (okay, not the Mercedes, but that one's not supposed to be a long- term car anyway.) The S70 uses synthetic, the Jetta (with almost 200K miles now- I started using synthetic in it when I bought it 6 years ago with 85k on the clock) and the 850 (That car had 250,000 miles when I got it, but it also needed all shaft seals except the rear main, so I didn't see much risk in switching after changing all of those.) But I'm undecided on the 740, simply because of the possibility of leaks in a 20 year old car with over 200,000 miles.

 

You need to do some research on oils, you are dead wrong about older engine oils and older classification oils, for example.
An oil labelled and tested as Service SE, does NOT have to meet current Service standards, as it is not classified to it. A more current oil classification is definitely not necessarily better for an older engine. You should also read up on older rebuilt engines wiping out camshafts within 20 minutes of start up, due to lack of high pressure anti scuff additives in the oil. Many very experienced engine builders are (or were before they figured it out) having the problem.
As for synthetics extending time in service intervals, dead wrong. Oils are changed on time intervals due to sludge formation, retention of hydrocarbons and other contaminants. Synthetics are just as prone to retaining these contaminants as any other engine oil.

Regards, Andrew.

 

I suppose that older API classification oils might still be available in specialty shops, but I haven't seen them in years. And I know all of the "High mileage" formula oils on auto parts store shelves still meet the newer classifications, as opposed to the older. I assumed that that was what you were referring to. As far as any of the major oil institutes are concerned (API, ACEA, ILSAC, etc.) newer classifications supercede older ones- that is to say, they represent in improvement over the previous classification. Still, there's is a lot of debate from many angles out there on the assorted issues regarding oil. Synthetic or not, extended drain intervals, whether or not the additives used in older oils are better than those used in newer oils, etc. There's plenty of evidence to support all of these positions, and plenty that refutes all of them. Naturally, there's "partisans" for all of them. Clearly, we don't agree. But I too, have done a lot of research into oil quality and what's right and what isn't, and I've made my decisions based on evidence, as well.

As for camshaft wear on initial startup of a rebuilt engine... that is a very critical time in the life of a camshaft. Even on modern engines, if something's going to go wrong with a cam, it's going to be in the first 20 minutes. And on a rebuilt engine, there are 2 distinctly different issues in play, that need lubricants with 2 distinctly different properties- a new camshaft requires a lubricant to have very good anti- friction, and more importantly, anti- shear qualities to prevent sudden destruction. Piston rings, on the other hand, need more friction in order to properly "bed- in." A good engine builder knows these things, and tries to act appropriately. Sometimes, a high- moly assembly lube, applied liberally to cam lobes and cam followers/ lifters, combined with an oil that is suited to help break in rings, is all that's needed. Sudden camshaft destruction soon after initial startup is NOT a new thing. It's been a problem as long as there have been engines to rebuild. It didn't suddenly start happening when oil companies drastically reduced the amount of ZDDP in their oils. As for cams that are already thoroughly broken in, it's not anywhere near as critical. Do you honestly believe that all these redblocks with 500,000 miles on the original engine were all using API SE oil the whole time? No... they weren't. Sudden camshaft failure, on a typical passenger car engine, is almost always an issue that happens immediately after valvetrain work. It's NOT going to happen because you changed oil types. My Mercedes is a perfect example of shoddy engine building practices resulting in cam destruction. When I bought it, it was running on 3 cylinders with a loud tick, and the seller was certain that "it just had a collapsed lifter!" The head had recently been completely redone. I knew it was more than just a collapsed lifter when I got the car, but for the price I paid for the car, it was still worth it. Now, do you know how I know the guy that fixed the engine (it had had the timing chain break- common problem on that engine) had no clue what he was doing? For one, the head gasket had been coated with RTV. It's a conventional, fiber- graphite gasket, and the engine is a bi- metal, iron block/ aluminum head engine. And second of all, the camshaft- one totally flat lobe, and 4 others that were badly scored, along with their corresponding followers. It WASN'T a new cam- the guy most likely mixed up the followers. I replaced the cam, cam followers, and head gasket, and the engine is fine now. This is a 1988 model car, and the only thing I did with the cam was coat it in moly assembly lube, and then I ran it at 2,000 RPM for 10 minutes, as the cam manufacturer said to do. Most cam makers give similar instructions.

In the end, you and I could probably butt heads all day long about oil, and it's not going to change either of our opinions. What needs to be provided here is a simple, straight answer to the guy's question about whether to switch his older engine to a synthetic or not. Is a synthetic going to magically make his engine last another 100,000 miles? no- it isn't. It's going to last that long because of reasonable maintenance and the excellent design of the redblock. Will his engine leak as a result of him switching to a synthetic oil? it's possible. Will he see ANY benefits at all? Again- it's possible. Now, use this, and decide what's right for you.

 

All the talk about oil and hyper oil changing (3,000mi intervals) is way off base when it comes to Volvo red blocks. Has anybody ever had a problem with a red block that wasn't overheated? Bottom end problem? Didn't think so... You'd better change your coolant and tranny fluid--much more important preventive maintenance in an older Volvo than engine oil. The last thing that will go is the motor UNLESS it was overheated or run out of oil. BTW, I have gone to full NAPA synthetic oil for a couple of years on all my Volvos and 7,000 miles intervals, and I am very happy with the results...

 

Not here to argue, just to add my experience with my 1992 940. Used Castrol 10W-30, changed every 5000 miles. Retired the car at 484,300 miles, engine still running strong. I tried synthetic for 3 changes in a row and saw no benefit, only increased cost.

 

Was your 940 a turbo or naturally aspirated?

I have a 2009 S60 2.5T and am wondering whether or not to switch to full synthetic from the Castrol GTX that they use by default at the Volvo dealer.

Some say full synthetic is better for a turbo because it can dissipate heat faster as well as withstand higher temperature.

But if your car was turbo, and you retired it still running strong with nearly a half million miles, well, then I don't know what to do.

 

S60 motor is nothing like the 940T motor. If I were you I'd use ONLY synthetic oil in that car-you don't want sludging...

 

I understand what you are saying tedv, but I must admit that this entire conventional vs synthetic debate has me confused.

One would think that if synthetic was that much better for my S60 2.5T then Volvo would require it, but they don't. Volvo recommends Castrol GTX, and isn't that a sludge resisting oil? At least that's what all those commercials say. ;-)

Anyways, I think the next change will be full synthetic. I did one change at 3,750 miles using Castrol GTX. The 7,500 miles change will be my switch to full synthetic.

By the way, once going to full syn, does 7,500 miles sound like a reasonable interval for one who's driving is not really considered extreme conditions?

 

What the manufacturers require these days is confusing; for example many european brands don't mention anything about changing the ATF. I am not sure what the idea is but if you ever drop the ATF after 100k in an Audi you will be scratching your head-it's like tar! Basically they are making cars which are not intended to last the way they used to, and once the warranty is up, who cares, that's my theory. Anyway, synthetic oil is in many ways superior to mineral, and the cost works out to be about the same since it is ok to prolong the change interval if using full syn. The 3k mile thing is a bit of a scam in my book, promoted by oil companies and service providers anyway, and so with the synthetic you could go easy 7-8k miles... Turbos especially are prone to sludging, coking, if you will, due to the higher temperatures and oil lines in which you tend to burn, "coke" the mineral oil easier than the syn. The VW Passat with the 1.8t has been in the news about exactly that problem and in that case VW started NOT requiring syn oil at first but then after thousands of sludge cases, now they do. Granted, the Passat 1.8t has other inherent flaws but the oil is major. Also, as with all turbos, some precautions should be taken such as a cool down period after high speed driving to allow the oil to continue to circulate and cool the turbo...