Oil change freq

[cr4a]

The manual for my 95 Civic says that I only need to change the oil every 7500 mi. My oil change place recommends every 3000 mi. I've been following the manual's suggestion, but now that I'm up to 140k mi, I'm not so sure.

Any suggestions?

[CivicSpoon]

Most people do 3,000 miles, especially on older cars. It's better to do it 3,000 miles, but this is coming from a person who just did an oil change after 7-8,000 miles. But chances are if you do it at 7,500 miles, you need to check the oil level regularly to make sure it doesn't get too low (when some burns up).

[superbluecivicsi]

follow the manual and some common sense.

[BullShifter]

7500 mile interval is for "normal conditions" in my opinion normal conditions DO NOT EXIST.

3000 mile interval is for sevre conditions which is what 99.9% of us deal with.

If you want to do it every 7500 miles upgrade to synthetic, mobil makes a 7500 mile oil. Even with regular synthetic I still change mine every 3000 miles.

[polacek]

I would not switch to synthetic as you have 140,000 miles. The reason is that synthetic will clean your engine and all the seals really good. You do not want that because over time the seals collect gunk from conventional oil. That creates seals in places where an oil leak can occur. I have not only heard about it, but had witnessed it twice. Stay with conventional and chang it at the 3,000 mile mark. The other thing about waiting until 7,500 miles is that the oil gets physically dirty. The oil may not break down, but fine particles that enter the engine via the air intake will cause damage. If you are leaking oil, go to 10w30. After that, seals need to be changed out. That's my btw, I use chevron 5w30 with Walmart's cheap oil filter. As long as the filter is changed out every time, it doesn't matter if you use a cheap filter or an expensive one. That's my opinion and can back that statement up with an engine that has 235,000 + miles and not a drop of oil lost.

Dennis

[typerx7]

change your oil within no more than 3500 miles on the oil. it is very bad for our little engines to be running on crappy, burnt oil for a long time. I chnage mine every 3000 on the dot. u should do the same. my car has 150,000 miles

[polacek]

I'm not sure that you must change it at 3,000 miles on the dot. Does it really matter if you have a 100hp 4-banger or a V-8 with 400hp? They all have pistons and valves which have tight tolerances.
I have read extensivly on this topic. One reason oil breaks down is from water. Water is generated in the engine at startup when the temperatures are below freezing, that would be condensation. That is why there is a breather which is connected from the engine to the airfilter intake. When you idle, the acidic and water condensation are removed from the engine through that breather. So, in the winter months it is a good idea to have the car idle for about 20 seconds to remove the fumes. As far as changing oil, in the winter months should be as close to 3,000 as possible. In the spring and summer, you can be a little lazy. The oil does not break down as easily since there are no water from condensation in the summer time, at least in Colorado.

[typerx7]

the main problem though is not the factors that affect the oil breakdown and viscosity but the reality of it burning off within the alotted time between oil changes. Once oil gets to a certain point it loses all detergents and it's ability to lubricate properly. Things like water and air bubbles can decrease the oil's ability to lubricate, as you said. but without the proper amount of detergents, the oil breaks down, burns off and keeps the engine parts from being lubricated. The main difference between 4bangers an v-8's may not be such an obvious one though. 4cyl engines run alot hotter and move alot faster (not the car just the engine, haha) per cycle than the larger v-8s do. v-8s require more oil because they are bigger not because they need more lube. In a d15 engine, at 135,000 miles, oil primarily loses it's detergents around 2300 miles. i know, that sucks, but i've tested it. So the factor here, to consider, is the heat that the engine creates and how much that oil inside can handle. If we were able to add grease in our crankcase rather than oil, then it may be a different story.