I switched to full synthetic oil last december. It's been 8 months. However I've not gotten to 5k mile on the oil yet. Only drive car on weekends. So when changing synthetic, should I go by time and not mileage in my scenario?

 

You certainly have to consider time, but with a synthetic you definitely have more immunity to deterioration than you would with plain old dino oil. The best way to be sure will always be to send in a sample for analysis, but that being said, with only 8 months and 5k on your current fill, I can't imagine that you wouldn't still be good to go for many more months and thousands of miles.

 

You'll see a variety of answers to your question from every 4K miles to 10K on cars with over 100K miles on their clocks. I only average 5K miles a year so it's a time thing for me and I change Mobil1 10W/30 with WIX twice a year. (OCD) What brand filters do you use?
Gary

 

I am still regular oil from the dealership and i been changing mine every 5k miles since 08. so far it been about 6 month and i still have another 1200 miles to go till i change it and i am Super charged. My parents change there oil every 10 w/ the synthetic. one car get change every 6 months do the amount of driving and the other car get changed out every 2 years b/c it sits in the garage most of the time. you should be fine every 10k

 

Since you're in the NE, I'd do it at least twice a year regardless of miles. You could rotate 5W/10W depending on the season to help those cold starts.Full synth gives you a little leeway but just gotta be consistent.

 

Time is definitely something to consider.

Used oil contains a lot of contaminates, that over time begin to form an acid in the oil that can damage bearings, seals, etc. Wouldn't hurt to be proactive and get some fresh oil in there from time to time

 

Mobil1 Extended Performance is a 15,000 mile interval. I've used it since I got the car at 30k miles and I use the Mobil1 filters. Never had a problem and I get 23-24mpg right now in a combination of highway/city driving, which is as good as the day I picked it up.

 

They still set a time limit for that oil. No more than 12 months.

 

Very true, forgot to mention that. I drive about 20-25k a year so for me it comes up regularly. I wasn't paying attention to the OPs question, just thinking about mileage.

 

I recently changed to Amsoil, the rep told me 10-15K miles or 12 month change interval, whichever comes first.

I put about 20k+ a year on my car also, and have been doing 5k intervals on Castrol GTX dino oil previously.

 

MANY factors figure into an oil change interval. Age of car, miles, how do you drive it? Type of oil.

Synth oil will go longer in MOST conditions.

Take my truck, I drive it over a hundred miles 5 days a week. I change my oil at 7500 (sometimes 10,000) miles, I use M1 5W30 extended life. I use a M1 M110 filter (will fit all VQ motors) It has 157000 miles and I cannot detect ANY oil usage between changes. But in my case I get the engine warmed up and cook out the water and gas contaminants in the oil twice a day 50 minute drive. This makes my oil last longer and it keeps acids and other things from eating up the engine. If you "only drive it on weekends" but you drive it at least 30 minutes at a pop, you are good. If you just fire it up and run to the corner store and back, you leave water in the oil and the exhaust system that will contaminate the engine. You should change synth oil every 5000 to 7500 (recommended by MOST manufacturers) miles or every 6 months which ever comes first. PERIOD.

 

I've heard on the first synthetic oil change, you should make sure to change your oil the next time sooner than you otherwise would. This is because synthetic oil can often clean out certain deposits left by conventional oil.