Greetings to all....

Would like to hear from knowledgeable sources what the justification is for changing the oil every year if the suggested life span has not been reached ( 10k) ? If the motor is not running it's not creating contaminants and the detergents have not been exhausted.

 

I think if you are truly interested you could conduct your own research by taking periodic oil samples to one of the Labs.

My two examples that I can list;

1) I used to have a company vehicle (Chrysler) that, for some reason, was never entered into the maintenance database. I drove it for 114K miles with 2 oil changes. When I gave up the vehicle the engine ran perfect, hardly using any oil.

2) Once I noticed a Real Estate lady's car dropping thick, black oil on my driveway. I called it to her attention and asked her when was the last oil change. She looked at me with wide-eyed surprise and told me NEVER. She had close to 100K on the car (Olds) at that time.

I used to have regular lab tests done on my engine oil when I owned a Lamborghini. That, because I was worried as the model had a reputation for scattered engines. Only one single time was something out of order. The Lab Technician asked me if I was driving in sand as he found too many silicone particles in the oil. Initially I said, "No Way" but, later I remembered driving a single loop around my block without my air filter elements.

 

Temperature and humidity changes cause condensation inside the block. The water causes steels to rust and aluminum to oxidize. The droplets run down the inside of the block into the bottom of the oil pan carrying those contaminants. I sent an oil sample from my boat that sat all winter. Contaminants were off the charts. I started filling the block (gallons of cheap oil) for the winter and all parameters were normal in the spring.

 

Partly it's that many people drive reasonably often BUT short distances. That means the oil doesn't get hot enough for long enough and water etc is left in it.

At the price of oil, going with the recommended change policy has got to be "good enough". But yes you could have it tested and that would probably be better, though maybe more expensive.

I bet any decent manufacturer is conservative (i.e. you could go a bit longer between changes) except maybe on those cars they're trying to sell as pretty much maintenance free to fleet buyers. (Does that even happen much with Jaguars?)

 

Oil has always been cheap and doing it myself was part of the fun of owning a specialty car. It took me a few years to go from 3000 mile changes to 5000 mile changes. Then I was reluctant but finally changed from pulling the plug and draining the oil to vacuum extraction of the oil. I guess maybe my next move will be from DIY to having the dealer do it. I find usually a clean engine will stay clean (on the inside) with regular oil changes. All of my cars that I bought new had clear oil after 5000 miles . After that I start to get concerned about the contaminates so until I see the data I'm sticking with 5000 mile changes.

 

When I bought my Jag, I talked with the Service Manager at the Jag dealership about oil change intervals. He recited what the Owner's Manual says but he also admitted that he changes the oil and filter in his personal Jag every 10,000 miles. He said that with modern-day computer-aided engine tolerances, coupled with today's far superior quality of oil & oil filters, every 10,000 miles is very safe. Even with him having said that, largely due to the relatively low cost of an oil change, and for no more than I drive my Jag, I change the oil (Mobile 1) and the filter (K&N) in mine every 6,000 miles ... just to play safe.