Oil changes and severe service

Mileage between oil changes and severe service

It’s time to get up to speed on oil changes and severe service

Carmakers used to recommend oil changes every 3,000 miles. But oil chemistry has improved a lot and engines have improved dramatically. Now, many car makers recommend oil changes every 7,500 to 10,000 miles using synthetic oil. However, that recommendation isn’t universal because oil life depends not just on miles driven, but also how you drive and which engine you have. For example, the oil in turbo engines tends to run hotter and that increases oxidation and viscosity improver breakdown. So you’ll often find a recommendation of oil changes every 5,000 to 7,500 miles for turbo equipped engines.

How you drive affects oil life

Most car owners refer to the maintenance guide and read the best case scenario for oil change recommendations. But they don’t often read the fine print where it talks about “severe service.” “Normal driving” oil change intervals are based on ideal conditions with long highway trips rather than stop and go driving and no trailer towing.

Recent studies show that 80% of drivers don’t drive under normal conditions. Instead, they drive short trip (less than 4 miles, especially in cold weather) in stop and go traffic. Those driving conditions degrade oil additives more quickly than highway driving. Short trips are especially hard on motor oil because a cold engine introduces more raw fuel, soot and condensation into the oil pan. When driving for long periods, the engine heat can force the evaporation of the fuel and water and a warm engine doesn’t produce as much soot. But short trips chew up the detergents, anti-oxidants, corrosion inhibitors and viscosity improvers much more quickly.

Oil level affects oil life

The car maker recommendations assume that you regularly check the oil level and top off whenever needed. The vast majority of drivers don’t do that. All engines burn some amount of oil and with the extended oil change intervals used by most drivers, it’s not uncommon to discover that your engine is low on oil.

Think about this: if you don’t check your oil level and top off when needed, you actually reduce the oil life of the remaining oil. In fact, driving while down a quart can reduce the life of the remaining oil by as much as 25%. That mean by the time you change your oil at 10,000 miles, you’re already overdue for an oil change by 2,500 miles!

What is severe service?

Now let’s talk about the fine print. I’ve already said that 80% of drivers don’t drive according to “normal” schedule. So what exactly is severe service?

• Repeated short trips of less than 5 miles (8 km) when temps are above freezing.
• Repeated short trips of less than 10 miles (16 km) with outside temperatures are below freezing.
• Operating in hot weather in stop-and-go “rush hour” traffic.
• Extensive idling and/or low speed driving for long distances, such as police, taxi or door-to-door delivery use.
• Driving in dusty conditions.
• Driving on rough, muddy, or salt spread roads.
• Towing a trailer, using a camper or a car-top carrier.

According to the Filter Manufacturers Council, severe driving is defined as

• Frequent idling for long periods of time, such as stop-and-go driving in heavy traffic. Many vehicles are subjected to this condition twice a day in commuting to major cities.

• Sustained highway driving in hot weather, such as vacation travel. Extended highway driving under hot conditions contributes to oil oxidation and viscosity improver breakdown.

• Towing a boat or trailer, frequently hauling heavy loads or carrying heavy objects on a rooftop rack.

• Driving in dusty conditions, such as dirt or gravel roads.

• Prolonged operation at sub-zero temperatures.

• Driving on steep hills or mountains on a regular basis.

What’s the lesson here?

1)      Most drivers fall into the severe service category

2)      Most drivers don’t check their oil level and top off when low

3)      Oil life depends on more than just mileage. It includes how you drive and which engine you have (turbo equipped engines are much harder on oil)

4)      No one can tell you how often to change your oil unless they know what engine you have, how you drive and how often you check your oil dipstick.

©, 2020 Rick Muscoplat