While the standard recommendation is to change your oil every 3,000 miles, it’s not always necessary. You can safely extend the length between oil changes if you drive your car most frequently on the highway in moderate temperatures or if you drive your car gently. The reason our mechanics recommend the standard 3,000 miles stems from seeing the difference in vehicles that have been serviced regularly and those that have been neglected.
Standard indicators of neglect are plugged oil passages or oil pump inlet screens, lifter or other engine noises, stuck piston rings, loss of oil pressure, premature engine wear or failure. Some engines are more forgiving than others. Some can withstand the abuse to over 100,000 miles while others may show symptoms by 50,000 miles. Your local City Garage mechanic can help you determine which is the best case for your car.
Engine oil carries metal that has worn away, dirt and moisture from the air and combustion gasses that gets past the piston rings and sludge from chemical processes.
These materials increase friction on metal parts and seals and causes seals and gaskets to harden.
These contaminates also dilute and wear out the additives in the oil that maintain viscosity and counter sludge formation. Changing the oil in a vehicle at the appropriate drain interval is the easiest, most cost-effective insurance against lubricant-related engine damage.
Why change oil frequently when not due by mileage?
Vehicles routinely driven short distances, especially in cold weather will build up moisture in the oil from condensation and combustion gases by-passing the rings. This build up of water will cause acids to be created within the oil resulting in the formulation of sludge and accelerated wear.
There are additives in the oil, which are designed to combat these acids, but they deplete over time, and can only control so much moisture. It can be worse to drive 2,000 miles in the winter of short trip driving in six months before changing oil than six or seven thousand in the same period.
Oil viscosity can make a big difference when it comes to getting lubrication to the furthest parts from the oil pump, which is usually the valve train. Besides improving gas mileage, if it gets near or below freezing where you live you should definitely be using a 5w-30 oil.
Consider this: 5w-30 takes 10 seconds to reach the valve train at 15 degrees Fahrenheit, compared to 20 seconds for 10w-30. Even worse, while 5w-30 is flowing freely in 40 seconds 10w-30 weight takes up to three minutes. Even better, consider switching to a synthetic oil, which will flow freely in 15 seconds at 15 degrees.