Know Your 2-Cycle Motor Oil:

Most frequently asked questions about snowmobile motor oil

January 2005 Feature Scott McQueen Viewed 17641 time(s)

Q: My two-cycle engine is not new. Can I use any non-detergent 30-weight oil or do I have to use a two-cycle type oil?

A: Regardless of age, two-cycle engines can benefit from the use of oils designed specifically for that type of service. Two-cycle oils are intended for consumption during the fuel burning process, thus they must be specially formulated with additive chemistry and base oils which tend to leave minimum amounts of ash. Two-cycle oils are also pre-diluted for easier mixing and more complete combustion.


Q: There are many different brands and types: how do I know which two-cycle oil is right for my engine?

A: There are two basic categories of two-cycle engines: liquid and air-cooled. The liquid-cooled category is comprised of outboard motors, personal watercraft and a number of snowmobile engines. Two-cycle oils for water-cooled engines are labeled with a symbol from NMMA (National Marine Manufacturers Association) and are given the designation TC-W3.

The air-cooled category includes motorcycles, lawn mowers, generators, pumps, chainsaws and weed trimmers. Two-cycle, air-cooled engine oils are marked with just the API (American Petroleum Institute) TC designation.

"TC" stands for two-cycle, "W" means water-cooled and "3" designates the most current generation of two-cycle water-cooled oils.


Q: Are all two-cycles oils marketed for my engine the same?

A: No. But if you select your oil by the NMMA or API identifications discussed above, you are less likely to make the wrong choice. Oils that have successfully passed the NMMA or API requirements for TC-W3 should display the symbol and indicate the license number somewhere on the package. If one of these designations is not shown, the oil may not meet the specification and has not been licensed or approved under the NMMA or API.

Q: Who is the authority for clearing two-cycle oils for sale?

A: For two-cycle oils identified as TC-W3, NMMA licenses a supplier based on data submitted from test procedures. For oils labeled TC, claims are made based on guidelines defined by API. For oils that do not carry either of these designations, you have only the claims made on the container or accompanying literature. In short, products without these designations are not monitored or approved two-cycle products under NMMA or API for entry into the marketplace. Therefore, consider trusting a supplier brand of proven performance when making a decision to buy.


Q: My mechanic/dealer tells me I must use only the OEM oil brand that matches the brand of equipment I have or my warranty will be void.

A: No. You are not limited to the purchase of only this specific brand of oil. For example, you might buy a new outboard engine and wish to use an oil such as Phillips 66 "Injex" instead of the OEM brand. On the label, you should find the proper API designation and NMMA symbol. This will indicate that the oil has been approved and licensed by the same company that built the engine and is fully approved for warranty use. An owner's manual should tell you to look for oils bearing the NMMA symbol (under the Magnuson Moss Warranty Act).

Q: I have heard that all "red" two-cycle oils should be avoided. Why is that?

A: Color is an identifier and should not be used as an indicator of oil quality. Oil manufacturers have a choice of colors for two-cycle oils and some choose not to dye the oil at all. If you are using premix fuel and oil, color can be very helpful in determining if the mix has been made. Red fuel/oil mix does not contrast well with red fuel containers; thus, red has lost some support as the color of choice. The products in the Phillips 66 two-cycle engine oil product line, for example, are dyed purple.

Q: I understand that I should use twice as much oil if I use any brand of oil other than the one recommended by my mechanic/dealer. Why do I have to use twice as much?

A: There is often no documented information given by the manufacturer to support this statement or any industry information to back it up. Such a practice would cause an excess of unburned oil in the combustion chamber, leading to "ring coking" and premature failure. For Phillips 66 Injex, Synjex and InjexPro two-cycle engine oils, always use exactly the same fuel/oil mix as recommended by the manufacturer.

Q: I always put in a little extra oil each time so I can be sure I'm protected or, there's always a little left so I just dump it in. Is this good for my motor/engine?

A: You should mix the fuel/oil ratio exactly as the manufacturer recommends. Adding too much oil could lead to early ring sticking, which can cause premature engine failure. The reverse of this is mixing the fuel/oil ratio on the light side. This will lead to the lack of proper lubrication, causing piston scuffing and in turn, excessive engine wear. No matter what type of environment your engine is operating in, always follow the manufacturer's recommended guidelines for fuel/oil mixing.

Q: I had engine damage judged to be from lack of lubrication. Could it be the Variable Rate Oiling (VRO) system or the oil? Should I disconnect the VRO or change oil brands?

A: Probably neither. Most often there is a one-time occurrence of "no oil" or "too little oil" present. Oil itself would be a problem only if it were the wrong oil for the application. A fully approved oil used in the right ratio should lubricate properly regardless of brand or color. VRO systems can malfunction, but once repaired, are far more accurate, timely and precise in delivering a proper mix than any amount of time and effort you can put into the task. The return to a qualified oil and properly functioning VRO system is your best approach.

Q: What about synthetic two-cycle oils? Will I get better performance or extend the life of my engine?

A: Synthetic two-cycle oils have certain advantages and benefits over mineral based two-cycle oils. Synthetic two-cycle oils will have excellent low temperature flow properties ideal for winter time use. Synthetic oils are typically environmentally friendly as they are biodegradable and also meet the low aquatic toxicity standards. Synthetic two-cycle oils have a higher viscosity index over mineral oils, which means they burn cleaner, helping to reduce deposit build-up and spark plug fouling. Synthetic blends also have excellent low temperature flow properties. These oils also maintain a high viscosity, which helps reduce piston scuffing and bearing wear.

Q: My neighbor says he has always used "brand X" two-cycle oil and has never had a problem. My brother says he used "brand X" and had nothing but problems. Why is this? Who is right?

A: Probably both. Two different people with the same make and model engine can experience very different end-use results. Differences can include non-oil related mechanical failures, mode of operation, maintenance and care, contamination, etc. Oils are often credited or blamed for things that may or may not pertain to an oil's role in engine performance. If your brother used the same oil on the same type of engine but did not follow good mixing practices, you would expect him to get different results.

Q: I switched from "brand X" to "brand Y" and experienced engine failure in less than five minutes. Did "brand Y" have a bad batch? Will "brand Y" oil not work in my type of engine? My mechanic said he had heard of such things before.

A: These are "panic questions" which often arise after having experienced sudden unexpected engine failure that is unexplained and not yet investigated. Most often, when these questions are asked, the engine has not been torn down. Should a failure occur, the first step should be to have a trained service technician determine the nature of the failure. Most non-oil related problems are recognized by the mechanic at this point. If not, you should save all damaged parts and a sample of the fuel/oil mix. Start with where you purchased the equipment to see what advice or solution they can offer. It may also be advisable to contact your fuel/oil supplier. With the information gained at this point, you should have your questions answered. There are a few points you may wish to consider for possible future reference. If it happens quickly, it is probably not oil-related. Oil companies perform many quality checks and pull samples of product throughout the blending and packaging process. e

(EDITOR'S NOTE: McQueen is the director of automotive products for ConocoPhillips. For more information, contact the Technical Service Hotline 800-766-0050 or

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