Are there any additives that really work on oil leaks. I think i have a rear main leak. I havent even crawled under there but seen oil on the pavement
4.0
Jeep Wrangler
160,000
Auto
If the leak is very small, some additives will reduce or stop the leak. A major leak needs a fix, or ;like many, you can put a cookie tray with kitty litter on your garage floor. Most cars leak a little; just look at any parking lot near supermarkets.
Too much additive will damage your valve gear.
if the leak is minor then I would just keep a eye on it. You can either do oil changes a little more frequently or just check it every two weeks and top off the oil as needed.
A rear leak I would think is differential, or brakes. No quick fix I know of, but bigger issues if you don’t fix quckly. or did you mean rear engine seal? Could be a pinion seal if 4wd.
Just because the oil drips from the bottom of the engine, doesn’t mean the leak is at the bottom of the engine. Try to trace the leak to its source. It might be a cheap fix.
+1 to Keith’s post.
If you can’t find the source(s) there are UV sensitive additives designed for finding difficult oil leaks. Once added, they leave a train that lights up under a blacklight (UV light). Check at the parts store.
My wild guess based on the mileage is that you may have seepage past the valvecover gasket(s) and/or the oil pan gasket. These are normal, not serious, and if you’ll post back with the results of your investigation we can discuss the results.
Yes Sir Mountainbike. Will do…
Hey. I seen an old montesa for sale just down the road
Try changing to high mileage oil.
Suggest to avoid stop-leak oil additives or other “miracle” additives until you know the source of the leak. Those additives can sometimes cause other problems so best not to consider them unless you have the facts to make an assessment and decide they are the only alternative short of removing the transmission and installing a new rear-main oil seal. Even then, me, I’d probably go with the remove the transmission method.
I’m unfamiliar with the “Montesa”, but I’d first find out exactly where the leak is coming from.
It’s perfectly normal for engines that get old to begin to seep some oil past their valvecover and/or oilpan gaskets. That often gathers under the pan and drips small amounts, misrepresenting itself as something serious. It isn’t. I myself have some seepage past my valvecover gasket… to be replaced as soon as I get the energy. And on a day when the pain of old age is at a minimum. And the weather good.
Right now you have a vehicle with (a) minor leak(s). Who knows what the Montesa would have for surprises. People don’t usually sell cars because they run perfectly.
By the way, I second the recommendation not to use additives. High mileage oil should be fine to try, but additives can, and often do, create more problems than they solve.
@badbearing
Has the transmission pan been off in a recent decade? I’ve seen messes under vehicles that you’d swear were engine seals/gaskets or big problems that turn out to be old, hardened trans pan gaskets and old trans fluid.
Sometimes it’s hard to tell trans fluid leaks/drips/spots under the car from engine oil leaks. You have a better chance by catching some drips on your fingers that are clinging to the underside of the vehicle.
I had a bit of a mess starting under our old Impala, recently. It looked like a death knell. I thought it was motor oil from the engine at first and a trans leak, too. I took off the trans pan, installed a filter, chipped off hardened gasket chips, installed a new lively one, and filled it up with fresh fluid. I wiped off as much fluid on the underside of the car, too.
Voilà!
Now there are absolutely NO spots where the old beast parks on our asphalt driveway! None! And I found out the engine wasn’t leaking.
“Are there any additives that really work on oil leaks. I think i have a rear main leak. I havent even crawled under there but seen oil on the pavement”
I wouldn’t jump to conclusions. That was my first instinct, to think the worst. :neutral: It turned out I needed a fluid change, anyhow, and a gasket and filter. 
CSA
Hey. I seen an old montesa for sale just down the road
See if it runs…it’d be fun to mess around with.
;-]
If it is a few drops put a drip pan under it and monitor oil level.
I like to say that nothing works for that. I say to look for oil leaks from all other sources first and see if the oil pan bolts are loose first. I say good luck and I have also told people to get rid of their old wreck before it kills them. Take which advice is best and ignore that which does not apply.
If it is a rear main seal leak , I have read that Valvoline Max Life is pretty good at helping those .
Years ago…I used STP for stopping (slowing) oil seepage. It worked great on some engines. It also works great for lubricating engine bearings during assembly.
I believe the rear main seal on that 4.0 straight 6 is not a radial seal
Isn’t it one of those 2-piece “rope seals” . . . ?
If so, I believe the transmission doesn’t have to be removed to replace it. But the oil pan does, AFAIK
does high-mileage oil also slow down leakage rate on those types of seals . . . ?
You or someone else has to put eyes on this problem. When you tell us you have not even looked under the car, there is no way to help you with a diagnosis. And frankly, if you can;t even be bothered to look, I am disinclined to try.