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Risk of Extended Oil Change Intervals

Published Jan 21st 2011, 5:24pm by



Nothing in your engine workers harder than your oil. With hundreds of moving parts, and thousands of explosions every minute, it's no wonder that engine oil needs to be changed frequently!

You've probably heard the old rule of thumb: Change your oil every 3,000 miles/ 5,000 kilometers or 3 months, whichever comes first. But some car manufacturers have introduced extended oil change intervals. They figure that a modern vehicle driven under the right conditions can go for 5,000 miles/8000 kilometers or more between an oil change.

The key phrase here is "under the right conditions". If you look at your owner's manual, you'll see two different maintenance schedules: one for "normal" driving conditions and one for "Severe Service". Severe service driving conditions include stop and go, short trips, towing, hauling, hot, cold, and dusty driving. That's why at AutoNetTV we often refer you to the severe service schedule in your owners' manual, because, for most of us CA car owners, that's the way we use our vehicles in everyday life.

Recently, four of the largest auto manufacturers in the world have extended engine warranty coverage for engine damage caused by oil sludge resulting from longer oil change intervals. They found that real-world conditions require more frequent oil changes than the 7,500mi/12,000 km interval they were recommending. They subsequently recommended more frequent oil change intervals and proof of timely oil changes in order to qualify for the extended warranty.

Oil sludge is the culprit. Sludge is oil that has turned to a thick, jelly-like consistency. Sludge can block passages in the engine, preventing oil from lubricating vital engine parts. Parts wear more quickly and may fail prematurely.

Sludge is caused by several factors. The first one is simply - time. The engine oil is contaminated by exhaust gas that eventually leads to sludge. That is where the recommendation to change your oil at least every three months comes from. Sludge can also come from oil that gets contaminated by water from normal condensation. A few minutes of driving at CA freeway speeds allows the oil to heat up enough for the water to evaporate. The problem is we often run errands or take other short trips that don't allow the engine to warm up enough for the water to evaporate. This is especially true in winter. Sludge also forms when the engine gets too hot, causing the oil to breakdown. Stop and go summer driving, towing and hauling are all prime conditions for creating harmful sludge. And every engine has hot spots that create sludge.

Given all of these factors, estimating when to change your oil is pretty complicated. A couple of manufacturers have computer programs built into their vehicles that record the number of cold starts, how many times the cylinders fire, engine temperature and other factors. From that, the computer estimates when you should change your oil and flashes a warning. But what if you do not have a vehicle with this feature? How do you know when to change your oil? We're not sure you really can. Which is why it is better to be safe than sorry. 3,000 mi/5,000 km or three months - whichever comes first - talk with a service advisor at AskPatty.com, Inc in Thousand Oaks and see if that's a good recommendation for the way you drive.





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