I am curious if any engine additives are worth the cost....

IMO, mostly not, ................ with the exception of Marvel Mystery Oil, Trans-X, and Rislone. I use only when needed, not on a continual basis.

Interesting. Thanks. I'll look into those

Zmax can damage your catalytic converter.  It uses ZDDP (Pennzoil used to call it Z-7) and it has been removed from regular oil for this reason.  Almost all additives can cause problems in one way or another to a good modern engine, but if the engine is on its last legs due to high miles, poor maintenance or both, then one of them might give you a few more miles.  Otherwise stick to a high quality oil of the recommended viscosity and follow the maintenance schedule and you will be fine.

What's ailing your car, that you are looking at additives to fix a problem??

s'boarder, what problem are you having?

Sorry for the show reply. It is a 1999 legacy outback with 193xxx on it so I'm looking to get the most out of it. A little off the zmax topic, but the car has some hard shifting, a blown trailing arm bushing and I'm assuming blown struts. I recently acquired this case so I have no info on history, it didn't even come with a title. I love to work on this car and may even rebuild the engine if I have trouble down the road so based on the response so far I should just leave it alone and do regular maintenance... Right?

 

Once again, thank you everybody!

is the check engine light on?

 

automatic transmission?

 

KYB struts are the most commonly preferred. you can find DIY help here and elsewhere online for that.

There's a Thread about Lubricants & Additives, here:

 

~► http://www.ultimatesubaru.org/forum/topic/66817-lubricants-additives-myths-reality/page-3

 

IMO, mostly not, ................ with the exception of Marvel Mystery Oil, Trans-X, and Rislone. I use only when needed, not on a continual basis.

 

TransX is great for the Automatic Transmission... and might be the worst for the Differential in some Automatic Transmissions, on the Long Run.

 

Look here for detailed info & Photos:

 

~► http://www.ultimatesubaru.org/forum/topic/148220-automatic-transaxle-lubrication-the-differential/

 

Kind Regards.

when was the timing belt system serviced last on that car? You will bend valves if it fails. And it's rarely the belt that fails, an idler will seize or puke it's bearings.

 

if you suspect the car was neglected, or even just has normal build-up with age, nothing wrong with a throttle-body and maybe IACV cleaning, and a SeaFoam vacuum line or spray-nozzle treatment.

 

many people like Marvel Mystery Oil treatments too, mostly for hydraulic lifters I guess.

 

Techron seems to actually work. not sure it's better than SeaFoam in the tank though...

 

Subaru Coolant Conditioner can help slow/stop/prevent small coolant leaks - ONLY install per bottle directions - ONE bottle max. (if you drain and re-fill the cooling system and swap any parts, ONLY use an OEM style thermostat - there IS a difference)

 

Edited March 16, 201511 yr by 1 Lucky Texan