When it comes to finding out whether drivers should use engine flush products or fuel additives, the internet will send you round in circles. Some say the products, added to a car’s oil or fuel to clean the engine’s internal moving parts and boost performance, are worth their weight in motor-protecting gold. Others claim they’re not worth the time or the effort.
The basic theory behind both these kinds of products is that by running them through the engine, you’ll clean out any deposits left by the engine’s combustion process. Proving whether they work is easier said than done. Here’s what the experts say.
Engine flush: Why having a cleaner engine is beneficial
Nick Reid, Green Flag technical expert and the company’s head of transformation, explains why someone might want to clean their car’s engine: “The dirtier an engine is, the less thermally efficient it will be. Deposits on the pistons and in the combustion chambers will drive up hydro carbon emissions. In a petrol engine this will mean the catalytic converter will have to work harder and so will have to be replaced sooner.”
Engine flush: What an engine flush maker says:
“STP Engine Flush is specially formulated to rapidly dissolve harmful engine deposits and maintain efficient oil circulation throughout the entire engine, helping to protect vital engine wear surfaces throughout the flush.”
Engine flush: The retailer’s point
Dave Swaysland, fuel additives expert at Halfords, said: “We’d advocate using engine flush prior to an oil change to remove sludge and other contaminants from key parts of the engine. Using engine flush prior to changing oil means that you’re cleaning the entire system and not contaminating the new oil that you’re about to put in, keeping your car running smoothly. Clearly the longer you leave it between oil changes the more important using an engine flush is. Also the older the car, the more chance of sludge build up.”
Engine flush: Could lead to warranty woe, says Ford
We asked Ford for its view of after-market engine flush products. It said: “Do not use oil additives or other engine treatments. Under certain conditions, they could damage the engine. If you do use one and there is a subsequent engine problem, your warranty will no longer be valid.”
Engine flush: Why car makers do not recommend them
Engine flush and additive products are essentially chemicals. These then react with any leftovers in the engine to strip them out. In the case of a flush, you empty them out; for additives, any waste is burnt off. The reason car makers don’t approve is that they’re concerned some of these chemicals may react with rubber or plastic components in the engine and cause premature ageing and failures.
Engine flush: Verdict
Green Flag technical expert Nick Reid said: “These products really are a case of ‘you pays your money, you takes your choice’. I believe some have a pure placebo effect on drivers: they see a positive result because they want to justify the lengths they’ve gone to. Some products may offer some marginal gains in performance. But I don’t think a regular, everyday driver will see a huge difference.
“If you really want to keep your car working as efficiently as possible, I would suggest you’ll be just as well keeping on top of your oil and filter changes. The cleaner your filters are, the cleaner the inside of the engine will be. It’s simple: the more dirt you let in, the more dirt you’ll have to clean out. If you look after your engine with regular servicing, you really shouldn’t need to do any remedial work.”