I often have conversations at the shop about oil changes. There are a lot of different opinions and as a result a lot of confusion. But the reality is that oil changes are a very necessary part of your Subaru’s longevity or lack thereof if not done as often as needed or done with poor quality parts.
All car manufacturers have a normal and severe maintenance schedule, and if you’re driving habits fall into the manufactures definition of normal then maybe it makes sense to follow that schedule. But if you use your Subaru or any other car you drive in any fashion other than starting it up getting on the freeway where you travel at freeway speeds until you reach your destination where you shut it off and then repeat this use in this fashion the majority of the time you drive it, than you do not fall into the normal maintenance schedule. The real reason for the different maintenance schedule is to give the appearance of having lower ownership costs.
I have heard to many times that a customer thinks that changing the oil every 3000 miles is something a well known lube center dreamed up. The marketing of the 3 month or 3000 mile oil change service was taken to new heights by the lube centers, but they sure didn’t dream up the idea.
When I started in auto shop we learned that the hardest thing an engine goes through is the heat of the summer and the cold of the winter. You should start the summer season with fresh engine oil and once the summer is over you should change the contaminated oil out of the engine as the excessive heat can be detrimental to the effectiveness of the oil. Conversely the engine should start the cold of winter with good fresh oil and sometimes a thinner grade of oil should be used to help the cold oil get to the top end of the engine quicker. Once the winter season is over the sludge that once was oil should be drained out. There you have it, the 4 oil changes a year your car should have.
I know there are companies out there telling you that if you use their synthetic oil you can forgo the 3000 mile thing. I have heard customers and read forums on line talk about having an oil analysis done to prove the oil was still ok 5000, 7000 and even 10000 miles from new. But is the oil filter still working? Does oil that still has lubricating properties mean that it is ok? While synthetic oil can stretch out the oil change interval the level of the oil should be monitored very closely regardless of the product used. The other fluid levels in the car such as the coolant need to be topped off periodically as well and the tires inflated too. If the service interval of the oil is stretched out the service of the rest of the car suffers as well.
How does the whole system work? Oil lubricates and cools the engine; in fact the oil in your engine is about 1/3 of your engines cooling system. As the valves open and close, the pistons move up and down it is oil that keeps the moving parts moving easier. The engine is the hub of your car it all starts with the rotation of the engine, the easier the job the engine has of all of its parts moving freely the easier all of the parts the engine is in turn supposed to turn will move as well. Yes slacking on oil changes poses ramifications to more than just the engine itself.
As the engine is injecting fuel into the cylinders to provide the explosion that powers the engine not all of the fuel is burnt, we do not achieve 100% combustion with the internal combustion engine. The excess fuel slides past the piston rings and into the crankcase where it mixes with the engine oil. Over time a lot of excess fuel can end up in the crankcase. The fuel mixed with the oil can degrade the lubricating properties of the oil and lower the flash point of the oil as well. Another words the longer the oil is in the engine, the more fuel it collects, and as this oil fuel mixture is used to lubricate the parts in the combustion chamber the more likely it is to burn away, out of the engine into the exhaust and out the tail pipe. Over time the engine can burn a significant amount of engine oil. Next fuel is a solvent that can and will eat away at seals and gaskets causing leaks that will need to be repaired. Try pouring a thimble full of gasoline on asphalt and watch how easily the fuel eats away at the road. Imagine what contaminated oil can do over time to the head gaskets in your Subaru.
There are systems in place designed to help remove the fuel from the engine oil, one is the positive crankcase ventilation system or PCV, the other is called the breather hose, or breather tube. On a Subaru you will find a rubber hose attached to each valve cover gasket and then traveling up to the air intake tube.
Here is how the system should work, once the engine oil gets up to temperature the fuel vapor and contaminates can separate themselves from the engine and this vapor can be pulled back into the intake manifold and be re burnt or introduced back into the combustion chamber. This helps clean up the engine oil and prolongs the oils life.
Here is the problem with this, if you get in your car and make short trips, or spend a lot of time “idle” in traffic this is never going to happen in your car. And this is why maintaining your Subaru based on how YOU use it, is the only way to get as much value out of your car as possible.
Ask yourself if you think the car companies really want you to keep your car 10 years take care of it and have it last or buy another car every 4 years.
Next imagine that you own a factory with rows of equipment that all needs maintenance on a regular basis or the chance of the equipment failing and costing you money and down time will greatly increase. Do you think most informed business owners will follow a strict schedule to maintain the equipment, thus keeping profits high and replacement costs down or rather roll the dice and stretch it out. The similarities are there.
Except that we often get caught up in this crazy notion of blue book value dictating how much money we should put into a car instead of looking at replacement costs or the total value of keeping what we already own in good shape so it will last, but that is another article to write at a later date.
Here are some pictures of a 1997 Subaru Outback 2.5l Engine with less than 100k on it that had engine oil leaks at every possible location. The owner admit tingly changed the oil every 7500 and has no idea what kind of oil was used. The sludge build up is not good at all. Over ten years the $500.00 or so in savings by stretching out the oil changes has been more than made up in mechanical repairs.
Thanks for reading