Additives: helpful or harmful?

by Jim KerrBackyard Mechanic . Sep 30 2016

Question: I would like your opinion on additives such as injector cleaners, oil enhancers, etc., under brand names such as Duralube or Lucas as examples. Do they actually work? Are there any benefits to using these products in your vehicle? Thanks, Fred

Answer: There has always been controversy about claims made by specialty chemical companies regarding the benefits of their additives. While there have been some “snake oil” additives sold in the past, only those that actually help remain in the marketplace for extended periods. There are many types and makes of additives for fuel systems, engine and transmission oils and even cooling systems. Let’s look at what they can do for your vehicle.

Fuel system additives for gasoline engines fall into two categories: those that mix with any water in the fuel system to prevent it from freezing (typically called gas line antifreeze) and Injector cleaning additives. Both work. Gasoline from the filling station does contain additives to help clean injectors but different brands of gasoline have different amounts and chemical formulations of their additives. If your vehicle is experiencing poor performance, hesitations or hard starting, an injector cleaner additive may help.

The injector cleaner additive dissolves and removes deposits on the tip and injector ports of the injector, so the injector spray pattern is correct again. Because the aftermarket additive is concentrated, it cleans faster. When technicians clean injectors in their service shops, they use an even more concentrated cleaner that is plumbed directly into the injector lines to do the same task but quicker.

Diesel fuel additives often also contain an anti-bacterial formula to slow the growth of fungi in diesel fuel that has been sitting for a longer time.

Oil additives also have different purposes. Some contain seal softener additive to help soften old and hard seals so they can seal better. This does work in engines and transmissions, but if the seal is broken it needs to be replaced. There is no such thing as “mechanic in a can.”

Other oil additives increase the viscosity of the oil, making it thicker so the oil doesn’t leak past piston rings and valve guides as fast. This is likely the least useful type of additive.

Many additives include anti-wear and anti-friction chemicals, especially useful on older engines with non-roller lifters but help reduce wear in any engine. Keeping clean engine oil with regular oil changes is most important but the additives will help.

For cooling systems, the additive to stop leaks probably does more harm than good. It may seal a leak but can also block other small passages in the system as well. The best cooling system additives neutralize acids in the coolant and include a lubrication additive to help the coolant flow and lubricate water pump seals.

Additives do help and are a huge part of the automotive aftermarket industry. Please read the label to make sure you are getting the additive type you need for your vehicle.


Question: The driver’s side power window on my 2011 Chevy Malibu will start to go down but then stops about halfway, then it won’t go up or down for a few seconds. And then starts moving again. Why does it do this? Thanks, Suzanne.

Answer: Power windows have electrical protection built into the circuit. In most newer vehicles, the circuit breaker is built right into the motor unit. If there is too much drag on the window, the power window motor has to work harder and slower. If too much electrical current flows through the motor at slow speeds, it can overheat and burn the motor out. To prevent this, the circuit breaker is opening the circuit till the motor cools.

The repair is to reduce the drag on the window itself. After removing the interior door panel, the window mechanism can be lubricated with a white grease and use a dry graphite powder on the window channel guides that the glass runs in. Because the car is not that old, the old lubricant is probably still good but there may be a misalignment of the window in the frame. There are several adjustments that can be made to align the window better and then it shouldn’t stop partway down. If it still does, then the window motor will need replacing.