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Old 28-01-2012, 12:00 PM   #41
DavoAust
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I'd do 10,000km changes in the 3000... but it runs too hot and sees high rpm too often to risk it. I like my big end bearings in once piece

This is possibly the most educational thread on agt in a while
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Old 28-01-2012, 12:39 PM   #42
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if the oil is crap then there's that risk
but if the oil is good and have a high HTHS (high temperature/high shear) rating, then it is NOT a problem
crap oil shears out of grade to a lower viscosity, and will also break down at higher temperatures... so in otherwords, a low HTHS rating

shearing happens due to mechanical stresses to the oil, such as with flat tappet valvetrain or tight bearing tolerances

modern engines run hotter than ever, and ACEA A3/B4 requirements as well as ILSAC GF5 requirements have strict requirements for oils suitable for these engines

used oil analyses by many people have shown that after 12000km, a good quality but affordable (ie: not boutique brands such as Motul or Red Line for example) still have a high viscosity and high base number as well as very low wear metal count... this is indicative that the oil has life left in it.... most analyses of 16000km drains have shown that the oil still have a safe margin left (good till 20000km), even for those run in extreme climates... but for the sake of peace of mind instead of trying to stretch things too much, 16000km is a good safe number for quality oil
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Old 28-01-2012, 01:27 PM   #43
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Ok so with this talk ? of 16k, where did the 6 month interval arise from? I.e. 10k or 6 mths.my car has been sitting for almost that long with a start every week or so, but I cannot see any logical explanation for the time based servicing.
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Old 28-01-2012, 01:37 PM   #44
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the time based intervals are ASSuming that you drive lots of short distances.... the engine doesn't get hot enough to burn off water condensates in the oil, and also because the engine fails to get hot enough, fuel dilutes the oil which compromises its operating life

now if you're like me who drives their car for a good distance (16km or more) but seldomly, then you can throw this rule out the window and just change the oil based on mileage


those intervals were mere guidelines and recommendations for the general populace... if you're educated and smart about cars, then you can ignore them and safely make your own determinations
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Old 28-01-2012, 01:43 PM   #45
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ok thanks ed. pretty much all of my trips are short and fast. so the 6 months or so of everyday use would be a sensible option. (or again, is this mainly based on older tech oils, and could be increased to 9 months or so? safely?)
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Old 28-01-2012, 01:50 PM   #46
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yeah, probably.... go get an oil analysis done to be very sure
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Old 28-01-2012, 02:17 PM   #47
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doing longer oil changes isnt a issue anymore as the man has said before oil has improved heaps, look at brand new cars now my lancer is done every 15000kms and i think falcons are 15000-20000 you do want your oil to look black at oil change if it still looks clean after 5000kms it is rubbish oil, the reason it goes black is from carbon, no carbon in the oil it has to go somewhere else which will be the sump for the pump to pick up and create more issues.
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Old 28-01-2012, 02:24 PM   #48
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oh yeah, I want to add that the climate matters a lot if you're driving short distances and have to determine a TIME BASED oil change interval

a hot climate obviously allows an engine to get up to operating temperatures faster and also reduces the possibility of water condensation in the oil due to the great dew point versus ambient temperature difference

so in other words, short distance driving in summer doesn't necessarily reduces oil life while short distance driving in winter does since 1) engine takes longer to warm up 2) higher water condensation possibilities
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Old 28-01-2012, 09:37 PM   #49
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I wouldnt mind changing from castol to something to see if the oil leaks on the 85 bf could improve
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Old 29-01-2012, 08:41 AM   #50
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Quote:
Originally Posted by laserlynx View Post
you do want your oil to look black at oil change if it still looks clean after 5000kms it is rubbish oil, the reason it goes black is from carbon, no carbon in the oil it has to go somewhere else which will be the sump for the pump to pick up and create more issues.
or maybe 5000km is too early to change then?

also, if the carbon is in the sump, it'll come out with the oil at a change. it wont stay there and clean oil will come out only.

the only thing bad about clean oil coming out is the waste of money of replacing good still usable oil.

---

i got a few more questions for the masses:-
there is a pouring/25C viscosity, a 40C viscosity and a 100C viscosity, does:-

pouring/25C = if valve stem seals a worn, and blow oil smoke at startup, look at changing this?
40C = the lower the better for start up protection?
100C = if blowing oil smoke at high rpm, look at changing this?
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Old 29-01-2012, 09:06 AM   #51
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smoke only at startup is usually bad valve seals out, worn cylinder bores, or bad piston rings... you can try a high mileage oil that has seal conditioners that may make the rubber pliable again and "fix" the problem, but you can't fix any wear and tear.... the smoking stops once the engine warms up because everything expands with heat and "seals" in place

smoke at high RPM is usually from crankcase blowby.... in other words, issues with the piston rings or PCV system

as with all things, try the cheapest fixes first and work your way up... if it's just the matter of a dodgy PCV valve or clogged air filter that's causing excess crankcase pressure causing VISIBLE oil consumption (smoke), then the fixes are easy and obvious
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Old 29-01-2012, 09:10 AM   #52
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some additional reading for the curious who want other opinions regarding oils:
http://forum.miata.net/vb/showthread.php?t=445965

it's a recent active thread of many oil threads on miata.net, which has a dedicated section for lubrication
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Old 21-07-2012, 06:03 PM   #53
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Thread might be dead but I thought I'd share my oil story and see if someone can help me decide! Story goes...

I purchased a Familia GT-R (BPD-1.8T) with 140,000 on the clock about 4 months back. It is in immaculate, and I mean IMMACULATE, condition! Stock apart from pod filter and 3 inch exhaust. Previous owner swears by Penrite 10W30 Mineral Oil and has used it since he owned the car - from circa 80,000 kms old out of Japan. He was changing every 2500kms and said it never used a drop and there is no reason why that is not true given the condition of the car and the credibility of the previous owner. I noticed that after about 4000kms that it may have used a bit of oil but it could have been the previous owner only filling to min level on the dipstick to conserve/save oil quantity due to his high change intervals. Anyway, I read A LOT of stuff on oils and decided to go to a 10W40 full syn Everyday from Penrite. That oil is now superseded by a Penrite HPR 5 5W40 full syn which has almost identical 40C and 100C vis numbers so I am about to order a 20L drum of the HPR 5 5W40 Penrite full syn. By the way, just out of interest, vis numbers of this oil is closely matched with Mobil 1 5W50.

This is what I have found so far running the full syn;
1. I had lifter noise at cold start with the original 10W30 after about 3000kms on that oil. It had been changed before I took possession of the car so I believe that to be fairly accurate. I checked the oil level and it was just above the dip stick low line - which in my opinion is too low.
2. New oil in and it seems to rev smoother around the 4000 - 5000 rpm range. Much quieter in my overall opinion but there is most probably lots of placebo going on in my head I am sure.
3. Turbo response is better, seems to come on quicker and the car seems a little more spirited around the 5K rpm range.
4. No more startup lifter noise. Not even a peep. On the previous oil the first time the lifter noise reared it's head was when I had to replace the lower crank pulley and belts. It took me a long time to get the belt tension correct so I was starting and stopping the car over and over as I re-tensioned, then started to check squeal, stopped the car, then re-tensioned, then started to check squeal ect ect. After I finally got things right I took the car for a drive and it had lifter noise all the way up to temperature - I was seriously gutted. Luckily, once it was warm and I got some revs in the engine (once I knew the belts were right) the lifter noise slowly abated to nothing and then only came back at cold start and occasionally cold idle (only on the colder mornings) about 1000 kms later.

Driving style is pretty nana like most of the time and I go 30 kms highway (3K rpms all the way) to work and back daily. I like to take it out a few weekends a month on more spirited driving occasions through hills and around bends where I boost the car and am consistently driving between 3-5K rpms. This would be around 200 to 300 kms twice monthly. The engine doesn't seem to get hotter - says oil temp sensor - She just enjoys the thrill of putting the power and grip into to the road for me as only a GT-R 4x4 can!

So the question is (for TheMAN I guess), is the 5W40 a good choice for the age of engine (Turbo BP with 140,000 kms) and type of driving I mentioned in 15-35 deg C ambient temps!???

Penrite 10W30 Mineral
40 deg C vis: 68 cSt
100 deg C vis: 10.6 cSt
Penrite Everyday 10W40 Full Synthetic
40 deg C vis: 97 cSt
100 deg C vis: 15.1 cSt
Penrite HPR 5 5W40 Full Synthetic
40 deg C vis: 92 cSt
100 deg C vis:15 cSt
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Old 21-07-2012, 06:23 PM   #54
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5W40 is perfect for your needs... you may even want to find a quality 0W40 oil too
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Old 21-07-2012, 06:57 PM   #55
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5W40 is perfect for your needs... you may even want to find a quality 0W40 oil too
Thanks for the quick reply! I was pretty sure I'd got it right. Will have a look for the 0W40 but quite sure now I will order the 5W40 Penrite HPR 5!
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