Oil Debate Mileage vs Longevity

[martyb]

Here one for the oil experts. Scenario, the Viper owner does an oil change with Mobil one in April, puts about 2000 miles on the car for the next 7 months. Checks the oil at the beginning of the 8th month, still looks new. With only 2000 miles on the oil, is it best to change the oil, or drive another 1000 or so miles??

Basically, is the oil breaking down while it is sitting in the oil pan not being used? I have a friend who only changes his oil in the springtime on his vette. He only puts about 1500 miles per year on his car. He contests that oil sitting in his oil pan on his car is no different the the oil sitting on a shelf in the store. Not sure if I agree.

martyb

 

[V 10 MAFIA]

I don't think oil can go bad like milk sitting in the fridge, especially synthetic. As it is encased in the motor, it is not exposed to any contaminating elements.

 

[martyb]

So, oil that has been in a car for a year(synthetic) that only has about 1500 miles on it should be good for another 1500 miles or so??

 

[94RT10Ohio]

I change my every winter, part of my hibernation time. It only gets about 1K on it a year. Considering it is less that $50 to do a filter/syn oil change I think it is worth the $.

 

[ViperRay]

Oil should be changed annually, even if the car is not driven.
I don't recall the details but there are contaminants and breakdown that occurs even without the engine running.

 

[luc]

The answer is a little more complicated.

As a result of the combustion process, moisture,fuel and other by-products end up in the oil and form and acidic brew.

The only way to "remove" most of those by-products is to boil them off by having the oil reach a temperature of at least 212*.

So, if your oil never have a chance to reach this temperature ( driving the car only a couples of miles,etc)I will use the time based schedule

But, if the car is driven long/hard enough for those by-products to boil off, there is no problem with changing the oil evey 12 months.

Luc 00GTS

 

[Chuck 98 RT/10]

So, oil that has been in a car for a year(synthetic) that only has about 1500 miles on it should be good for another 1500 miles or so??

Probably but it isn't going to be as good as a freshly opened plastic bottle. As Ray and Luc pointed out, blow-by and other contaminates in the motor are breaking down the oil.

 

[Tom F&L GoR]

Luc is correct. Most of the fuel and moisture can be driven off, although blowby, the additives in the gasoline, and the higher end of gasoline will remain because their boiling point is beyond 212F/100C.

Even well-running engines have blowby and condensate entering the oil; the oil is really the engine's house cleaner. Water in the oil will combine with the additives and render them unavailable for their normal job - making the multiple short trip type of use one of the most difficult issues for formulating engine oil.

At least in my car, the oil temperature doesn't get over 200F for 20-30 minutes after the coolant is fully warmed up. Depending on the year, there are up to 10 quarts to heat up.

It also shows that if your driving schedule is short, it's better to change the oil before the long sleep rather than after.

To learn more about oil formulating, go to our engine oil page and click the "technical" button. It describes what goes into an oil and why.

 

[martyb]

Great info, thanks everyone.

 

[DEVILDOG]

Like others above I change my Mobil 1 and filter once a year in conjunction with the required annual inspection here in Texas. For me that is in April which is great for me since I have fresh oil in the car for the very hot summers we have here. In addition, when I drive the car(minimum once a month) I always let it warm up for about 10 minutes and then drive a minimum of 30 minutes on the highway at high speeds to fully heat up the oil and burn off contaminates.

 

[Schulmann]

Do you what instrument was added to the Gen 3 Vipers ? Oil temperature sensor. Viper is very ******* oil: engin, tranny, break. From personal experience: if you track race or you drive more then 10 hours consecutive (and pushing hard) then you should change your oil (engin & tranny) as often as you can. You should even carefully select the brand and viscosity. Point. If you are just driving around your house 2-3 times a year then you can survive with only one oil change per year. Otherwise follow closely what your dealer advise you to do. Vipers are great cars, the only thing that they ask for is oil change on regular intervalles.

 

[sbkim]

I am not sure if this means anything but I noticed that when I check my oil after car sits for several weeks and it's pitch black. After driving hard for couple days, oil looks little lighter in color. Both times oil was checked cold.

 

[GTS Dean]

So, oil that has been in a car for a year(synthetic) that only has about 1500 miles on it should be good for another 1500 miles or so??

I would say yes, if you take the car out for extended drives and boil off the condensed water accumulations. My GTS went about 1700 miles the past 2 years on no oil change. (Mobil 1, 10W30) I had an oil sample analysis done each year and noted no significant change in any of the readings.

Even when I was tracking my car HARD - 4 to 5 times a year, plus 2500 road miles - on Mobil 1 15W-50, I would go about a year between changes. Of course, I sampled more frequently based on driving conditions. Under heavy track usage, I would generally add about 2 quarts of makeup oil per oil change cycle. I most often found that fuel dilution was my chief concern - causing viscosity loss, and most likely, emissions increases.