I always thought these were a bad idea, but reading how they work, they slightly swell the rubber seals/gaskets so shouldn’t result in blocked oil passages.

Have slight leak in my car at the back of the engine which is dripping on the manifold causing burning oil fumes in the cabin when I’m stationary. Can’t see exactly where it is coming from without stripping down but suspect the valve cover gasket or camshaft seal.

Car is 10 years old, 103K and worth £5K, temped to tip a can of wynns oil leak stop in, anyone used this? What’s the worst that can happen😬

I wouldn’t, I would find the leak.

What is the car.

suspect the valve cover gasket or camshaft seal.

Those are usually relatively easy to access (compared to sump and crankshaft seals, anyway). I would try to see where it’s coming from and fix it properly before trying oil additives.

I’d live with the leak or fix it.
I’d be dubious of the claims and how it would affect the seals on the high pressure side.

Definitely fix it. Your £5k car is probably worth £6k now anyway. And what does a seal or valve cover gasket cost – £5/£10? Probably not much more than a can of additive!

It’s an XF,sorry meant crankshaft seal not camshaft. Garage reckoned £350 to replace it.

Much better to fix properly IMO. £350 bill on a £5K car is definitely in the “economical to repair” category for me. For a car that was/is marketed as premium/luxury, I would have thought that garage bills in the £hundreds should probably be expected from time to time.

I’d give it a go.

“Classic” engine oil usually has the same additives in by default and I’ve never had any issues in the MG.

It doesn’t leak anyway, but nothing goes wrong as a result of the classic oil.

Well, apart from a lack of ZTAP in even classic oils, but that’s a different matter.

A bit ghetto, but find the leak, clean it up and cover it with something like gasket seal compound, let it dry and see what happens, won’t cost much more than a few quid and a couple of hours work with the bonus of no additives in the oil.

Forgot to mention, the leak started just after I changed the oil, so did wonder if the chemical composition of the new oil could be to blame hence the interest in adding the additive.

I’ll probably replace with a newer estate when the secondhand market calms down so likely only going to keep another 6months.

Forgot to mention, the leak started just after I changed the oil

Did you change the oil filter too? If so, my money is on the oil filter not being correctly fitted. Sometimes the rubber O-ring on the old filter sticks to the oil pump. When you fit the new filter, the new O-ring fits on top of the old one. They will always leak. I would try removing the oil filter and checking everything carefully.

New oil could be thinner – did you use 0-30 or 5-30? In a car with a 100k I would not use the 0w unless I lived somewhere very cold. Most manufacturers specify a range of different oil weights depending on the temp range, and we live where there are the least extremes so
no problem with slightly thicker oil, 10w30 if you can get fully synthetic might well be the least leaky.
The seal swelling additives are part of normal seal “conditioning” additives in a few types of automotive oils – ATF for transmissions for example.
That quite for a crankshaft seal is very reasonable by BTW.

Did you change the oil filter too? If so, my money is on the oil filter not being correctly fitted. Sometimes the rubber O-ring on the old filter sticks to the oil pump. When you fit the new filter, the new O-ring fits on top of the old one. They will always leak. I would try removing the oil filter and checking everything carefully.

I did change the filter, but I think there was only an large o-ring on the plastic filter cover which I changed – I just put the new filter in the cover and screwed it on. If there was supposed to be a smaller o-ring on the filter I didn’t see it, though I guess it’s the larger filter cover o-ring that stops the leaking externally – I did check round the filter and it appeared to be ok.

The seal swelling additives are part of normal seal “conditioning” additives in a few types of automotive oils

Interesting, can’t be that harmful then?

New oil could be thinner – did you use 0-30 or 5-30? In a car with a 100k I would not use the 0w unless I lived somewhere very cold

Used 5-30

There are two main types of oil filters, cartridge and canister types. Canister types look like this:

The O-ring is attached to the filter. Sometimes they stick to the oil pump housing and tear away from the filter. If you fit a new filter without removing the old O-ring, you’ll have a new O-ring sitting on top of the old one. It will leak.

Cartridge type ones have a replaceable filter inside a removable housing. There will be an O-ring to seal it. You need to make sure the old O-ring is removed an a new one fitted correctly. If it’s not fitted correctly, it can leak.

Sorry to butt in, but kind of relevant. I have a very slow, like one drip per day leak from the gearbox. The opposite end to the clutch. Although there’s always the possibility it’s coming from somewhere else, but I’m pretty sure it’s gearbox oil. There looks to be a kind of plate on the end of the box and the oil is collecting at the bottom of this between the box and the plate. It’s a twenty year old VW banger so can’t be arsed to go removing the gearbox to fix it, but it’s annoying as I can’t park on other people’s drives. What are the chances that there could be a replaceable gasket behind that plate? I could remove that in situ, but don’t wanna be draining the box and jacking up the car etc if it’s unlikely to be coming from there? Failing that, would a bead of mastic/glue/sealant along the join bodge it for a while?

The seal swelling additives are part of normal seal “conditioning” additives in a few types of automotive oils

Interesting, can’t be that harmful then?

Unlikely to be harmful , oil and car manufacturers will never endorse additives for obvious reasons, you are looking for an enhancement to the seal environment, traditionally ATF was used as a seal swelling agent , there is no real way to tell if the seal has a physical defect due to wear/damage or has hardened and no longer grips the shaft without removal/inspection.
Personally I would research if it is a common problem on these engines – if so get the garage to fix it , if not try the seal treatment and keep a close eye .
Is it a timing end or gearbox end seal?

Blast it in I’m curious to see if it works, it can surely only do harm if it’s out of synch with the recommended oil for the engine.

Daft question, you didn’t ‘spill’ any did you when changing the oil. My car’s oil filter is driectly above the exhause at the back of the engine, so I always gat a little drip on the exhaust, no matter what I do. I’d trace the leak if you can with a torch. Be aware, with air flow etc, it can make it look a damn site worse as it just spreads any oil.

You could just live with it. Pretend it’s the 70s and your driving anything made by British Leyland.

Jags were part of Leyland group back then!

Is it a timing end or gearbox end seal?

It’s at the back, so gearbox end. It’s not really possible to see where it’s coming out without taking out a load of bits including the valance.

Daft question, you didn’t ‘spill’ any did you when changing the oil.

That was my thought initially but it was a good 3-4 months ago now so any spillage would have burnt off.

You could just live with it. Pretend it’s the 70s and your driving anything made by British Leyland.

I’d live with it if it wasn’t for that fact it fills the cabin a horrible burnt oil smell which I can’t imagine is good for you.

I’d check if the crankcase ventilation is clear before dumping a tin of snake oil in an engine. If the crankcase breather is blocked due to modern long oil change intervals then it’ll push oil out of crank/camshaft/rocker instead.

Fix it. Cars require maintenance from time to time and the older they get the more maintenance they need nd the running costs increase.

You can bung in some additive and it might work…it might not…it might make things worse. But even if it does work then the chances are it will be a temporary fix. You don’t know the state of the internals of the engine…are the oil ways coked up for example? If they are then there might be a risk of the sealing properties of the additive working in parts of the engine you don’t intend with the risk of starving parts of the engine of oil. Also the tests these additives are put to are often done on a perfect engine…nice clean engine to demonstrate the additive working…who knows what will happen when you bung it in a real engine coked up from years of use and abuse.

Crank seals, indeed any seal, does not last forever and need replacing eventually…if these additives were so effective and have zero downsides then why would any oil seal ever be replaced in any engine at all….ever?

Personally I would get it fixed and wouldn’t bother. Maintain your car properly, use decent oil and parts when maintaining and they will last forever.

I’d check if the crankcase ventilation is clear before dumping a tin of snake oil in an engine. If the crankcase breather is blocked due to modern long oil change intervals then it’ll push oil out of crank/camshaft/rocker instead.

That’s a pretty good shout RNP and I did go out first thing to check that, but the back of the engine where the breather runs is packed under the bulkhead and I was struggling to remove the trim and in a fit of annoyance I grabbed the Wynns oil stop which arrived yesterday and poured it in😬. Will report back on whether it works when I’ve driven it a bit.

Fix it. Cars require maintenance from time to time and the older they get the more maintenance they need nd the running costs increase.

But I’m a bit of a tight arse that enjoys shedding! If it was 2 or 3 years old I’d be getting it fixed properly, so in some ways older cars can be cheaper to maintain as you feel less precious about them.

Maintain your car properly, use decent oil and parts when maintaining and they will last forever.

This is generally excellent advice, but they will not last forever, no matter what you do. Parts will wear out, gaskets and seals will deteriorate and they will require more and more maintenance and repair. There’s no point spending much money trying to keep an old, high-mileage vehicle in tip-top condition. Eventually, it becomes more economical to just run them into the ground and get something newer.

Yes but buying a new car or even a newer used car has a significant cost associated with it…you either spread that cost with ongoing maintenance on your current car or spend it all in one go buying another car…which you still have to continually invest in to maintain, depreciate and keep in a good state of running order. The money finds you whatever you do…its the fundamental cost of motoring. The only reason to buy a new car is really because you fancy something else or need something bigger/smaller/more efficient etc.

But changing a car due to maintenance cost (engine/gearbox rebuilds or run away rust and rot aside) is not always a cost effective reason to swap cars…unless you get one with a warranty and/or service package thrown into the cost. And don’t forget newer cars are more electronic so come with far more risk of things to go wrong that are much more expensive to diagnose and fix than a crank shaft rear main seal.

Yes but buying a new car or even a newer used car has a significant cost associated with it…you either spread that cost with ongoing maintenance on your current car or spend it all in one go buying another car…which you still have to continually invest in to maintain, depreciate and keep in a good state of running order. The money finds you whatever you do…its the fundamental cost of motoring. The only reason to buy a new car is really because you fancy something else or need something bigger/smaller/more efficient etc.

No, at some point a car will cost more to repair it than it would cost to replace with a better used vehicle.