Dragon Oil And Lubricants,S.A
Just thought I'd share some of my knowledge with everyone to try to improve our community. This is my first of who knows how many issues (i guess) of things I have found people to commonly misunderstand or be relatively uninformed about. I've got a BS from Ferris State University in Automotive Engineering, for those who need a little evidence.
Contrary to popular belief... there is no need to change your oil every 3000 miles. It seems that every forum I've ever visited is filled with people who religiously follow the "change your oil every 3000 miles or your engine will explode" rule. And while this may have been the case 30 years ago, it simply isn't the case anymore.
Oil doesn't wear out. Plain and simple. Whatever you do to it, however long you use it, oil will never wear out. Rather, we replace our oil because one of two things happen:
Additives are used up - Oxidation inhibitors, extreme pressure additives, detergents, anti-wear additives, viscosity improvers and friction reducers are depleted or broken down over time. Each one of these additives only lasts so long in suspension in the oil before it must be used to do its job within the engine. Certain additives are broken down by extreme heat or pressures, while others are obsorbed into seals, used to capture contaminates, or used up within the metal parts of the engine itself. When these additives are used up, viscosity of the oil increases and lubricity of the oil decreases. This promotes wear within the engine and essentially renders the oil useless.
The oil becomes contaminated - Oil becomes contaiminated with water, dirt, fuel, soot, wear metals, acid and other by-products of combustion. This leads to increased corrosion and poor viscosity of our oil which can damage vital engine parts or cause sludge buildup. There are additives that capture and suspend these particles within the oil, which are then captured within the oil filter, but those additives only last so long. And once they are gone, the sludge and wear begins to form.
Many fleets and those highly dedicated to their vehicles use oil analysis companys to check their oil for life remaining and to see what contaminates are in the oil. This usually costs $10-30 per analysis and is mainly used to look for excessive wear and show signs of a failure before it actually happens. These analysis companys have provided data on all current oils meeting federal regulations, and the results have shown that oil changed at 3000 mile intervals (whether it be synthetic or conventional) isn't even half used up under street driven conditions.
30 years ago, when the 3000 mile rule was created. Oil additive technology was very poor and oil was not effective past 3000 miles. However, now oil additives remain effective for much longer, and in some cases (such as in some VWs) you can change your oil once every 12000 miles as long as you change your filter every 6000.
The best advice about when to change oil is to look in your factory service manual and go by what it says. Unless you are doing oil analysis, this is the only way to know you are getting the most out of your oil while still staying within the safe range. However the following is my basic recommendation for oil change intervals on a street driven vehicle:
Conventional Oil - 5000 miles.
Synthetic Blend - 7500 miles.
Full Synthetic - 10000 miles.
Remember that track driven vehicles, or race cars should have their oil changed more often due to extreme temperaures that cars on the street (or even drag cars) will not experience. These extreme temperatures break down the viscosity improvers and some other additives more quickly and decrease the life of the oil. A general rule is every hour of racing on a high performance synthetic = 1000 miles of oil wear.
Hopefully this knowledge saves you all some money.