Villiska

I have a problem I'd really like to find out about since this car needs to last me one more year before I can sell it and buy something else. To start off, this is the details of my car:

1999 Mustang V6
198,xxx Miles
Pretty much every bit of maintenance has been done on this car and done regularly. It runs like a champ.

Issue

Say I change my oil/oil filter today. I can go 2-4 months driving it every day to work and back (probably 30-40 miles driven a day) and my oil is fine. Then out of nowhere, two weeks later it'll be at the 1/4th mark. I'll fill it back up by topping it off as much as needed whether it be 1qt or 2qts and in 2-3 weeks it'll be at 1/4th again.

However, what gets me is, if I change my oil and my oil filter and do a full change, it'll last me another 3-4 months again before it gives me this issue. Now, I suppose I don't mind doing this every 3-4 months until I can sell the damn thing, but what worries me is how random it is. There's no leaks under the car in the morning or after work and there's no oil in my coolant or anything. I have no idea what's causing this. The first time this happened, I didn't understand what was going on and I beat the **** out of my lifters and got a lifter tick at idle for about 3 weeks and now it's gone completely. It happened again the other day when I got too confident in the oil level staying the same and I checked it when I heard an almost...turbo-like spooling sound when I started my car.

Also, I noticed this didn't happen in the Winter. I bought this car in October of 2013 and the previous owner didn't change the oil since February or so. I didn't change the oil until December because it was fine. Then it started getting hot outside and it's like it has oil diarrhea that won't stop. Should I change my oil from 5W-30? I've heard you should use 10W-30 in the Summer or something.

Anyways, I have no idea what to think. My friend is one of those "Run a Ford until it dies" kind of people and he's the only car savvy friend I have but he says to just keep doing oil changes every 2-4 months until I sell it and stop letting it worry me.

Any ideas?

Villiska

Also, the guy who sold me this car wouldn't dump it on me due to a new oil problem if you think that is the reason his oil was fine and mine wasn't. But another thing is, he used regular motor oil, I use full synthetic. Could this be an issue?

PNYXPRESS

The synthetic is a thinner oil than its conventional counterpart of the same weight so that may be the problem. The synthetic is able to leak around the rings and into the combustion chamber. Not sure why it last longer sometimes than other times though.

Fink

how did the previous owner drive the car? typical old person style, slow and rarely going passed 2500rpm?

ive ran into a few occasions where a younger person has bought a car off an elderly person and they had some issues due to the dramatic difference in driving patterns.

as far as the weight of oil to use, you use thinner oil(5w30) in the winter because it has a better viscoscity at ambient temp than 10w30. switching to the heavier weight oil in the summer is so the oil isnt too thin at ambient temp. I live in Canada and run thinner weight oil in the winter vs summer, due to easier starting/less bearing damage.

another thing is, you do 30-40 miles per day and you get issues after 3-4 months, which would be 2700-5000 miles in that time period. Synthetic is a better oil to use but it does break down over time, it could be that the oil is so broken down that the oil ring on the pistons cant do its job properly

dawson1112

You should be changing your oil at the 3 month mark any ways. You have a high mileage car.

High mileage+3 month old oil= starts to burn oil. If your not leaking oil, and your at your scheduled oil change , then just change it. Topping it off is not the way its done.

Villiska

The person prior to me drove it normally I would think. He wasn't the type to do burnouts or race people on the highway or anything, but whether or not he gassed it hard wherever he went is unknown.

Honestly I think I just had the wrong mindset from seeing other people's cars (2008+) only needing their oil changed 1-2 times a year, and when changing their oil, their oil level is the same as it was when they changed it but the oil is just old. I figured that's how all cars should be regardless of their mileage so I thought I had some big problem.

If I'm able to go 3-4 months before needing a change, I can afford that and for a 15 year old car with over 200,000 miles on it, I guess I can't complain that that's my biggest issue. Literally everything works in this car so I should see the glass more half full I suppose.

Villiska

Yeah, I mean I don't see any oil leaks or anything so that's good I imagine. I've never seen a puddle or even drops under my vehicle in the morning or after work. I didn't know high mileage meant burning oil, why is that?

Also, we have a few work vehicles namely an ISUZU box truck that is over 400,000 miles and doesn't burn oil. It just gets filthy and needs replaced. Is it just a matter of the motor in question or?

Daehawk

Maybe Im the only one but I dont trust synthetic for an older high mileage engine.

PNYXPRESS

I woulnt start running synthetic in a high mileage engine but I wouldn't stop using it in an engine that ran synthetic all its life just cause its high mileage now

Villiska

When I bought the car from the guy, in the trunk was a half and half mix between regular and synthetic but he only had the car for 2-3 years before me. I have no idea what it used prior to that. Would it be a good idea to go back to a half and half blend (I use Castrol and so did he) or stick with my full synthetic that I am now?

Also, what would be the latest time recommended for me to still use 10w30 in the warmer weather? It's coming up on September and in Virginia I don't think it'll be TOO cold until around November. Maybe a bit chilly in October. I'm due for an oil change though and will be doing one in the coming weekend when I'm not working.

Note, I haven't been using 10w30 at all this Summer and my oil issue started when the weather got warm. I use 5w30. Should I switch to 10w30 until my next oil change and then do 5w30 when it becomes really cold in like December and see how it fairs?