AMSOIL P.i. Review: My Fuel-System Cleaning Routine

My AMSOIL P.i. review after about 15 years of use

I have been using AMSOIL P.i. for about 15 years. It is part of the maintenance routine for my vehicles, including my daily-driven 2019 Ford F-150 with a Whipple-supercharged 5.0, my 2012 Shelby GT500 track car, and my former 2014 Toyota Tacoma TRD Off-Road with the V6, a manual transmission, and a King suspension lift.

I use it as an occasional fuel-system cleaning treatment. I keep my vehicles in good order, and I have not noticed a night-and-day change after using it. I do not have before-and-after fuel-economy measurements, injector inspections, or dyno results to offer. This review is about how I use it and why I keep buying it.

I am also an independent AMSOIL dealer. I may earn a commission when you purchase through my links, and yes, the dealer discount is a nice perk. You can read my dealer disclosure.

Why P.i. is part of my used-vehicle routine

When I buy a used vehicle, one of the first things I do is switch its fluids to the appropriate AMSOIL products and use P.i. to clean the fuel system. I had already been using AMSOIL before I bought the Tacoma, so that truck followed the same routine.

For me, there is value in establishing my own maintenance routine when a vehicle becomes mine. The F-150 is my daily driver, while the GT500 is a track project. They have very different jobs, but I care about staying on top of both.

The same thinking shows up in my oil changes. I have generally chosen intervals around 5,000–10,000 miles rather than trying to reach the longest advertised interval. That is my maintenance preference, not a schedule for every engine. My Signature Series 5W-30 review goes into my Tacoma ownership and oil-change routine.

What AMSOIL P.i. is designed to do

P.i. Performance Improver is an AMSOIL fuel injector cleaner and gasoline additive intended to clean injector and combustion-chamber deposits. The current 12-fluid-ounce bottle is product APICN-EA. AMSOIL lists it for port-injected and direct-injected gasoline cars and trucks, including E85 use, with a bottle designed for capless fillers. It is not for diesel or two-stroke engines.

Those are manufacturer specifications. They describe the product’s intended use; my ownership experience does not independently measure its cleaning performance.

How often I use P.i. versus AMSOIL’s directions

My own routine has been roughly every 10,000–15,000 miles as an occasional maintenance clean. AMSOIL’s recommended interval is every 4,000 miles. I want that difference to be clear: my routine is an account of what I have done, not the manufacturer’s recommended schedule.

I do not use the absence of an obvious change in how a vehicle runs as proof that it needed no cleaning—or that a treatment accomplished a particular result. With a well-maintained vehicle, my reason for using it is peace of mind.

How to use AMSOIL P.i. at a fuel stop

I add P.i. when the tank is close to empty, immediately before filling up at the gas station. It fits easily into a normal fuel stop.

1. Read the current bottle directions and confirm the application.
2. Add the entire 12-ounce bottle at fill-up for up to 30 gallons of gasoline.
3. For a larger tank, AMSOIL specifies two bottles; it advises against more than two bottles per treatment.
4. Fill up and record the mileage for your maintenance notes.

Source for application, dosing, and interval: AMSOIL P.i. technical bulletin. Check the current label when you buy a bottle.

AMSOIL P.i. vs. Upper Cylinder Lubricant

These products fill different roles. P.i. is the periodic treatment for cleaning existing deposits. Upper Cylinder Lubricant is an every-tank gasoline treatment intended to maintain injector cleanliness while adding lubrication and corrosion protection.

That is why I think of P.i. as an occasional cleaning step. It is not the every-fill-up product. AMSOIL explains the distinction in its P.i. and Upper Cylinder Lubricant comparison.

Is AMSOIL P.i. worth it to me?

Yes, for the way I approach maintenance. My truck cost around $55,000 when new. In that context, an occasional bottle has felt like a reasonable expense to me. I am comfortable with that choice even without a dramatic change in the way it drives.

I have described maintenance as “cheap insurance,” but I mean peace of mind. I cannot tell you that a bottle prevented a repair or saved an engine. I can tell you that I have used P.i. for years and continue to include it in my routine.

If you are deciding whether it is worth buying, start with what you want it to do. My experience is with occasional maintenance use in vehicles I take care of. It is not a test of whether an additive can fix a particular drivability problem.

AMSOIL P.i. price and where to buy

Check the current AMSOIL P.i. price and availability in the official AMSOIL store. This is my dealer link. AMSOIL handles checkout and shipping; its listing shows current package options and offers.

If you order AMSOIL regularly, my Preferred Customer guide explains the membership option. Compare its cost with the savings on what you actually expect to buy.

For help choosing a product, send me your vehicle details and what you are trying to accomplish. Include engine modifications and the fuel you use.