Oil Burns after prolonged use?

[EloManga]

I have a high compression 2.5L V6 Mazda engine and I've noticed that once my oil hits over 3000Km's of use, it starts to burn and/or disappear. I don't believe I have a leak, well not one that requires I add 100-300 ml's of oil per week anyway. Currently I'm using Valvoline Synthetic, 5w30. It has about 5000Km's of use now, but I'm doing highway driving, so I hope to have a longer oci.
Is this common or does it just mean that I need to change my oil? When it's fresh, I don't lose a drop.

 

[Blue99]

This issue of oil consumption later on in the OCI interval seems to be common with many vehicles. It could be attributed to the additives wearing out that are providing heat and oxidation resistance for the base oils.

But if you are running a Grp III synthetic, it should have good high temperature performance.

Is it possibly a PCV valve or a ring sticking problem?

 

[JAG]

This happens often. In my VW 1.8T engine some oils show this tendency more than others. I steer away from the oils that show it more than others. I do NOT think it's a really bad thing but if it can be avoided, might as well since burning oil isn't good for anything. Since you are in Canada, perhaps you consider using Esso XD3 instead of Valvoline Synpower 5w30 and see if that phenomenon lessens or disappears.

 

[hominid7]

My car has the Mazda 2.5 ltr KL V6. I've never had any problem with oil consumption. Then again, i've never gone over 3000 miles either

It sounds like you are using the right vis and a quality oil, so not sure why you are having problems.

Have you checked your spark plug wells for signs of oil leaking from the valve cover gasket? As Blue99 suggested, check the PCV valve, pull it out and shake it, it should rattle. If not, replace it.

These tend to be very reliable long-lasting, smooth running V6's. They are a short-stroke design, so we do run slightly higher RPM's on the highway than other similar sized V6's, but i've run mine 75-85 MPH for 4-5 hours at a time with the A/C running, without any consumption at all.

I've tried just about ever brand of oil in my car and the two that come to mind as very good performers are Castrol syntec Blend (Semi-synthetic) and good ol' Motorcraft. Both in 5w30. My engine feels sluggish when i use anything thicker than 5w30.

I'd also recommend using an OEM filter. Buy them at your Mazda dealer or I buy them in quantity online for about 4 dollars a piece. They are Nippon filters, made in Malaysia, exact same as OEM.

Last weekend i cleaned the throttle body intake and was surprised how much gunk can build up in their after only 10,000 miles since i did it last time.

 

[m2200b]

These motors will carbon up pretty easy and raise your compression even more if not lift your head gasket too. Bad PCV will do it remarkably fast. I'd use techron at least twice a year or regane as I'm not sure which is available in Canada.

 

[EloManga]

Well, I have 2 Pure 1's left, hard to find in Canada and got a family member to purchase on their last trip to the usa. Would Wix be better? It's basically Fram, Wix or K&N up here. K&N is pretty expensive also.

 

[Gary Allan]

Go with the Wix. Get a used oil analysis to figure out what's happening to the oil at the fatigue stage. I vote for shearing.

I can figure no reason why XD-3 would produce any more noise upon start up compared to any other like visc oil.

 

[Cutehumor]

here's what I do, after 3k, oil consumption increases. the 10w30 I use is probably shearing. so I top off with 10w40. I find the oil consumption slows to a reasonable amount. not only that. It helps me to extend to 5k changes.

 

[buster]

It's perfectly normal for you car to consume some amount of oil. Some even say it's a good thing. Highway driving for sustained periods of time will increase the consumption in many cases.

 

[John K]

I had this happen with an 87 Taurus 2.5L 4 cyl, didn't seem to make much difference with type of oil I used. I used whatever oil was on sale. I kept this car for 200,000 miles, and would change it around 3000. If for some reason I went past 3000, and it was 1 qt low, if I added a quart it would burn another qt in, say 1000 mi. I figured the additives were used up.

 

[miked2]

I had an 81 Plymouth (remember those) Reliant with a 2.2 engine. In 2500 miles after an oil change, it would be a half quart low. By the 3000 mile mark, it would be a full quart low. I changed it regularly @ 3000 miles, except once I let go to 3300 miles, it used another full quart in just 300 miles. I changed the oil & filter again & never let it go beyound 3000 miles again.
I never added any oil to it, kept it to well over 100,000 miles.
As John K said, I just thought all the additives were worn out. No BITOG back then.

 

[mechtech]

My old BMW 320i would not use oil until 2,000 miles were accumulated on the oil, then it would start using it. A dramatic change! I guess it just broke down into smaller pieces, and wore out the additives.
I used 10-40 and 20-50 at the time.

 

[EloManga]

Gary, well, I had posted about the problem I had with the XD-3 and though nobody supported my suggestion, I still believe this is what happened. Since XD-3 has so many cleaning additives, and the engine was on a slow boat from Japan, gunk was built up in it. So, the XD-3 loosened it and then came the screaming.
Actually, right now, since I don't have any Valvoline to add, I've been adding XD-3. Plus, they say it's thicker, so I thought that would help also.
If my oci is only going to last say 4000Km's, then should I bother using synthetic?
Right now there's 2 sales on. 1 is for Valvo dino, 5 bottles for like $11.50. Also, Shell Forumla 1 dino for like $1.50 a bottle. Would you guys recommend either of these oils for me to use?

 

[Gary Allan]

You guys in Canada are in a pickle. You really should use a synthetic in the winter ..just due to the severity of the temps. OTOH, it would surely seem like a waste to use a synthetic for short OCIs. For 4000km OCIs I don't think you can go wrong with any of the two oils that you mentioned. I've used older evolutions of Formula Shell and it worked well for me. I haven't used Valvoline for over 20 years.

 

[EloManga]

I will check the pcv valve. I did change it 2 years ago, but I've only put say 15000Km's on it since? It is possible, thanks for waking me up!

As for Esso XD-3, I used it for about 1000Km's and then I had to change because the engine was screaming after I didn't start it for 3 days. I got the engine flushed for carbon knock and then I had to change the oil. I am a little worried about it happening again if I try it. Actually, I used Mobil 1 10W30 and that actually didn't begin to start burning for a while. So it was the best.
Hominid7, You have 1 of 3 cars, Probe GT (which I have), MX6 or 626. I'm well aware of these engines. Mine is actually the J-Spec, KLZE, which is 10:1 compression, 197bhp. This may have something to do with the burning, as they are common for it, but I don't know. I'm using a Pure 1 filter, that is for a 95 ZR-1, it's bigger and fits. Incase you are unaware, there are 2 sites you can check out for more info on these cars, Probetalk.com or MX6.com. I'm on both, that's how I found out about the ZE.

 

[hominid7]

Nice engine! Mine is the stock KL in my 2001 626.

With that high a compression maybe the difference between 5w30 and 10w30 is enough to show its face after a few thousand miles. It would be interesting to see how 5w40 does in your engine. It's spec'd for xxw40 as this is one of the few Ford (Mazda) engines that they did not back-spec for 5w20.

 

[JAG]

I see. You must walk a fine line between the oil being thin enough at startup but thick & stable enough to not get burned up later on in the oil change interval. That can be a tough order in an area with a cold climate. I don't normally like this oil but Mobil 1 0W-40 may be able to achieve that balance. It has a relatively low HTHS viscosity (for a 40 weight) so won't hurt power/fuel economy much, flows relatively well in cold temps for decent startups, and has a relatively high operating temp viscosity (even after it shears) which will help control oil consumption.

The Pure 1 filters are great for filtration but I recall reading that they have pretty high restriction (issue during cold starts), so maybe you should consider a less restrictive oil filter (look into K&N for sure) too.

 

[Gilitar]

I believe that you are probably seeing shearing. I believe that GC is absolutley PERFECT for your application. It's a heavy 30 weight that is not prone to shearing plus it will protect you during the cold Canadian winter.

 

[EloManga]

GC? (German Castrol?) What does that mean cuz I don't know and please excuse my stupidity.
But why would my oil shear? I mean I'm not driving it hard and my rpm's, though a little high for me, are at 3000. It doesn't make sense. Unless it's got something to do with my engine in particular?
I mean I drove 6000Km's on XD-3, to Florida and back in a 99 2.4L Altima, and would you believe it didn't lose a drop and was clean when I got back!?!?
Please comment on the above, but maybe I'll get the Shell conventional and try it and then get some XD-3 and use it in the next change.
Though my engine specifies 5w30, do you guys think I should go with 5 or 10 conventional in the Shell?

 

[Gilitar]

GC is Castrol Syntec 0w30 made in Germany. I believe that you can find it at Wal-Mart since you are in Canada. GC is almost a 40 weight oil which means that it will help with your oil consumption problems. GC is also good for very cold weather being that it is a 0wXX oil. In my opinion this oil fits your needs perfectly.