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2015 Subaru Impreza WRX STi - Additives?

do oil additives work

Sometimes they do but don’t expect miracles.

What problem are you trying to resolve or improve?

What do you have in mind. Some of them can do damage if used under the wrong circumstances.

RRS rice racer syndrome.

That depends on what additives you are talking about and what you expect of them. The additives in motor oil used to prevent oil breakdown during the usual lifetime between oil changes certainly work. I suspect you mean some other kinds of additives, though.

I am interested in slick 50. Will it actually extend the life of my engine.


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Why did you not put that in your original post ? That way you would have had a answer 4 days ago.


Suggest to just use the oil the manufacturer tells you to use. The time to use an oil additive imo is when the engine is near the end of its operating life, pretty much worn out, showing symptoms. Sometimes an additive then will buy you some time before needing to replace the engine.

Forget Slick 50, use high quality oil, change it regularly. No additives needed.



That overpriced junk-in-a-can was proven to be a scam a few decades ago.


No, Slick 50 will not prolong the life of your engine, with a good chance of contrary.

Using the extra money you wanted to spend on Slick 50 to buy higher quality synthetic oil will have much better effect.

Also, consider doing some research into the particular synthetics pros and cons for your particular application.

For example, look at this study:

Sure enough, it promotes AMSOIL, but read between the lines and apply it into the practice:

So, yes, indeed AMSOIL has the least wear on 4-ball-test, but so do most of other oils, other than last 2, including overhyped Mobile 1 EP.
This is the most relevant test for your “I want to extend my engine life” goal.

If you need to worry about cold starts, I mean REALLY cold winter starts, pay attention to

Then, since it is Subaru engine, oil evaporation is a very important factor, as these things beat up the oil in their horizontally opposed design, make sure to use the lowest NOACK which works on other factors:

Now, making a summary, I would suspect that using Pennzoil Ultra or Valvoline SynPower just off the store shelf will give you the best balance for the “everyday inspired driving”, but if I’m wrong and you are into the racing, once again you can make a research of the actual oil specs (every manufacturer publishes them) and decide what is the best.

Your chances to have your engine in like-new health for a long time will be much better with the careful oil selection rather than “some oil” plus “magical” Slick50

The only one I have used is something called Tufoil . This stuff did work and any engine you used it in was noticeably smoother . That being said I havent used it in a long time as it was kind of pricey and I feel todays oils have evolved to the point where it probably isnt needed . I change the oil at 6000 mile intervals and it doesnt even look dirty at that mileage .

Designer oils are a waste of money.

Buy the cheapest oil that meets the specs for the vehicle.



Good read, would like to see an update comparing 0w20 synthetic oils.

I learn every day :slight_smile:
Not what I do not agree about “waste of money” part, but “designer oil”… nicely put :slight_smile:

I use SuperTech synthetic and I like it a lot: for the price of “designer” conventional I get something what definitely holds better over the change interval, which I do NOT extend.
So far my experience is good.
Initially I found about it from moderator who runs his R51 Pathfinder on it over 300K miles and ticking, decided “why not” and use it ever since on all my vehicles.