Best Engine Oil Additive (2026): 5 Picks Compared

Compared on paper

Specifications are manufacturer rated, as published on each listing and collected 30 October 2026. Where a listing contradicts itself, both figures are shown.

How the points were given

Each additive is scored on performance, build, value, safety and warranty, with the weights published on our How We Pick page. None states a safety listing, so all score zero on safety, and only one gives a clear warranty term.

Scores run from 9.2 to 9.8: each product’s point total is placed on that range, so more points always means a higher score.

What the listings tell you

We read 5 additive listings. Two stated a mixing ratio, and only one stated a clear warranty term. None stated a safety listing, and one listing contradicted itself on quantity. Sizes run from a 2 oz single treatment to a 32 fl oz bottle, and engine coverage runs from a single-purpose lifter additive to a treatment stated for gas and diesel engines, transmissions, hybrids and racing engines.

Choosing the best engine oil additive

Size and dose

Size alone does not set the dose. Prolube states 32 fl oz with a mixing ratio of 1 oz per quart for standard engines and 2 oz per quart for heavy-duty or high-mileage engines, while DNL states one bottle for every 5 quarts of oil. TriboTEX states a 2 oz treatment for one regular truck, tractor or small diesel, and the two Liqui Moly listings state no mixing ratio at all, so the dose is not stated for those picks.

Engine coverage

Coverage is where the picks split. Prolube states gas and diesel engines plus transmissions, DNL states gasoline, diesel, hybrid and racing engines, and TriboTEX states gas or diesel engines for old and new cars. The Liqui Moly lifter additive is narrower: it is stated for vehicles with turbochargers and catalytic converters, for noise caused by hydraulic tappets, rather than as a general treatment.

Maker claims and stated specs

Keep the two apart. Prolube claims wear reduced by up to 45 percent, and DNL claims friction reduced by up to 60 percent with heat resistance up to 1,800 degrees Fahrenheit (982 degrees Celsius). Those are maker claims, not stated results, and this guide reports them as such. Stated specs are different: sizes, mixing ratios, the 300 ml lifter size, the 0.3 liters LiquiMoly size, and the 180 days warranty term on the TriboTEX listing.

Warranty

Only TriboTEX states a concrete warranty term, a manufacturer warranty for 180 days since purchase. Prolube, DNL and LiquiMoly 3721 state no warranty term, and the lifter additive spec table reads only the word Warranty, with no term attached, so those picks score zero on warranty.

Garage Fit Check

• Check the stated size against the oil volume: Prolube mixes at 1 oz per quart, and DNL at one bottle per 5 quarts.
• Keep the 300 ml lifter additive for hydraulic tappet noise, which is its stated purpose, rather than as a general treatment.
• One TriboTEX treatment covers one regular truck, tractor or small diesel, per the listing.
• No pick here states a safety listing, so follow the directions on the bottle and keep the treatment with the oil supplies.

FAQ: garage tools

What is an engine oil additive?

An engine oil additive is a treatment added to engine oil. The listings in this guide describe friction reduction, cleaning detergents, wear protection and noise reduction as maker claims, with sizes from 2 oz to 32 fl oz.

When should you add an oil additive?

The listings give two timing cues: DNL states its treatment is best if used at every oil change, and Prolube gives mixing ratios for standard engines and for heavy-duty or high-mileage engines. No listing here states a calendar interval.

How long is engine oil good for?

No listing in this guide states a shelf life or service life for engine oil. DNL states its treatment is best if used at every oil change, which ties use to the oil change rather than to a stated interval.

Do engine oil additives work?

The makers claim results: Prolube claims wear reduced by up to 45 percent, DNL claims friction reduced by up to 60 percent, and TriboTEX claims a coating that reverses wear in bearings. The listings do not include independent results, so this guide reports those figures as maker claims.

Related: our engine and shop equipment hub, the best motor oil additive, synthetic vs conventional motor oil and the best diesel fuel additive.