Slick 50 Engine Additive And Transmission Additive: Product Review


Before Slick 50

Back in the day, circa 1967, Slick 50 had yet to hit the market in the field of engine oil and automatic transmission fluid additives. The only thing around and well enough known to be much discussed was STP, and STP has a lot of enemies. Stir a coffee break among auto mechanics and you’d find an STP hater or three. Clogs up the engines, they’d say, and that was the complimentary version.

Having been raised on a ranch where you learn to handle your own automotive maintenance from financial necessity, followed by two years of majoring in Auto Mechanics at Northern Montana College (since renamed Montana State University, Northern)…hey, I’d heard it all. Still, when my 1960 Chevrolet Biscayne sedan began burning oil at the rate of a quart every 400 miles, I had to do something. Clearly, either the used car salesman who’d sold me the vehicle had lied, impossible as that might be to believe, or the engine rebuild supposedly done a few months earlier had been botched.

Facing nothing but ugly options, I tried adding STP to the engine oil. Lo and behold, the engine quit burning oil, or nearly so. By the time the Chevy was down a quart, 2,000 miles had come and gone and it was time for an oil change, anyway. (Back then 2,000 miles was the recommended oil change interval, not 3,000.)

That experience left me open to the idea of engine additives in general. Decades passed without the use of any such thing after the Chevy was traded in some 56,000 miles later (and still burning no more oil than one quart for every 2,000 miles). Even so, when our 1991 Mercury Cougar began dangerously overheating on mountain passes in Montana in 1997, I was ready to listen to my wife. Pam had a deep and abiding belief in the benefits of Slick 50, that particular additive and that one only. Her ex-husband had for many years worked as a highly skilled technician specializing in imported engines. One day when a Slick 50 demonstration was in progress using a running engine with transparent block walls, she’d had the opportunity to join her (ex) husband at the shop to view the demo. She’d been mightily impressed.

I had a bottle of Slick 50 engine oil additive included in an oil change for the Cougar in Missoula. Thankfully, the Coug came with a full set of gauges, which meant we could monitor coolant temperature from moment to moment. After roughly 150 miles of travel following the oil change, the temperature suddenly dropped swiftly from “almost too hot to keep going” to “midrange normal running temperature”. That car was eventually repossessed, but not until a lot of ground had been covered. The car never threatened to overheat again. I was convinced.

There Are Plenty Who Disagree

There are hundreds if not thousands of folks out there who rant against any and all automotive additives with vigor and venom. They all seem to have just one key point: Additives are BAD-BAD-AND-MORE-BAD. To underscore that point, no matter which product they’re slamming, quite a few of them state as gospel that nobody has ever come forth to tout the benefits of Product X who didn’t have financial gain in mind.

Oh? I’ll admit I have avoiding financial loss firmly in my thoughts, but gain? I buy the stuff, which costs money. Nobody is paying me big endorsement cash as if I were a sports celebrity or even ten bucks up front to write this article.

I’m the first to admit my personal experience is anecdotal, not a controlled scientific experiment. But Pam and I couldn’t care less who writes nasty stuff about a product we treasure. What we care about is surviving in a tough economy, and Slick 50 helps to do that every day. Sure, it costs. Because of that, a bottle of transmission additive I’d purchased at Wal-Mart (which usually has the best prices for such) was still riding around in our Subaru when we started driving out of Colorado toward Utah and then Arizona.

The stuff wasn’t meant for the Outback but for the 1996 GMC pickup with over 160,000 miles on it. We were less than a hundred miles from our starting point when that vehicle’s tranny had to have help. It was losing transmission fluid rapidly and had already lost second gear. We still had more than 700 miles to go. Oh, did I mention that the truck also had to tow our cargo trailer filled to the gills with “stuff”?

Finally adding the Slick 50 to the truck’s automatic transmission allowed it to make it the rest of the way. That truck needed help and still does. We don’t have the money to have the thing rebuilt, and yes, it still leaks. But the leak slowed enough to get all the way to our Arizona property without breaking down and without having to add anything further. Now it’s out front, sitting there, staining the bunchgrass with transmission fluid and occcasionally hauling our larger generator 1/4 mile over to the well to pump a batch of water. But it’s here, and without Slick 50, it wouldn’t have been. It would have broken down along the road somewhere, towed by a wrecker to some repair shop’s storage yard, and likely have ended up being confiscated by the towing company as nothing but salvage.

Update: Our finances improved in 2010, allowing us to have the GMC’s transmission rebuilt.

Dang. This reads like a low budget infomercial! It’s not, believe me. No, I do not have stock in the company!! Don’t take my word for it–if you do try the product in your own engine or “whatever”, draw your own conclusions.

The Generator Story

We live off grid in an area permeated with horrendous desert heat. Our only electrical power comes from a pair of portable generators. The larger unit gets fired up only for appliances that draw a lot of wattage such as the coffee maker, microwave, and deep well water pump. The rest of the time–as much as 16 hours per day–we use one of the smallest generators on the market: A Yamaha inverter model that weighs only 27 pounds and has an automatic idle feature which drops the rpm’s down when they’re not needed. Matter of fact, that unit is powering this computer as I write, not to mention our 20 inch TV.

These generators are not made to be used the way we use them. We’ve loved these little Yamahas ever since using a somewhat similar model (though not an inverter type) for three full years while living off grid in Montana (1999-2002). Thing is, with less than three months of use we’ve already far exceeded its expected lifetime as claimed by Yahama. A label right on the machine says it’s good for up to 300 hours. Folks, we run it roughly 420 hours in a single month. And yes, we expect it to last for at least two and possibly three years of use.

No, we did not use Slick 50 in the Montana generator. The additive is not cheap. We quite frankly never thought to use it, not even once, despite using it in our motor vehicles nonstop. Within three weeks of opening the box from the manufacturer on this one, however, we could see–actually, we could hear–that our baby would be soon dead if it didn’t get help. It’s the heat, y’ see. Hardcore. The little beastie was already sounding “tinny”. We figured running long hours in high ambient heat had to be causing the damage.

So we threw the warranty in the trash and changed out the oil. Instead of sticking with the recommended 30 weight, the new mix consisted of half 40 weight (Pennzoil) and half Slick 50. From that time forward, the Yamaha has purred away happily from startup to shutdown, which often means from around 9:00 a.m. to 1:00 a.m. or even later.


1. Adding the product to an overheating engine (which was NOT having coolant problems) reduced the coolant operating temperature to “normal”.

2. Adding the product to engines in seven distinct and separate motor vehicles has never resulted in an engine problem that traced to the additive.

3. Adding the product to a 50cc Yamaha engine saved the engine from seizing up in desert heat without question despite going against Yamaha recommendations to use 30 weight motor oil only.

4. Although our personal experience has been overwhelmingly favorable, there are innumerable critics of the product whose writings are available online. As always, you’ll have to draw your own conclusions.

5 thoughts on “Slick 50 Engine Additive And Transmission Additive: Product Review

  1. When I moved this page over from another site, 79 comments had to be left behind. Those comments included dozens of favorable testimonials for Slick 50, some of them in the “absolutely amazing” category. Additionally, my wife and I have continued to gain experience with Slick 50 (all positive) in numerous engines in the years since this piece was first written.

    If you have (a) questions or (b) experience with Slick 50 (good or bad) that you’d like to share, feel free to leave your own comment, and we’ll go from there.

  2. most of the synthetic oils didn’t help for the engine lubrication. All groups before Group 5 are not synthetic. But they labeled as synthetic. All types of synthetic oils can be the best choice for some situations.

  3. Thanks for commenting, Frederick. I have little doubt you’ve got that right, that synthetic oils can be the best choice at times. In my case, I’ve never once used anything even “labeled” as synthetic. They cost more that tossing in some Slick 50, for one thing. For the other, I grew up using one or another of several “regular” oils, eventually (in my 20’s) settled in with Pennzoil, and just never have seen any real reason to switch.

  4. i have a dumb question. can i add Slick 50 high mileage transmission additive if the transmission is showing full? must i drain some fluid as to not overfill the transmission level?
    sorry for these elementary questions but i do not want to screw up my 2004 f-150 4×4.
    thank you. SA

  5. Scott, it’s never a great idea to overfill either a transmission or an engine crankcase. I’ve done it, and some machines are more forgiving than others, but yes; I would definitely drain some fluid first.

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