Interesting observation by switching oil brands

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Long post, and a bit of background. My truck has Mitsubishi's infamous 12-valve 6G72 (3.0L) engine, which burn oils due to the valve guides developing gaps over time. Whilst the issue was never addressed on the 12-valve, Mitsubishi resolved this problem by coming out with a 24-valve version of this engine and discontinuing production of the 12-valve model. Up until 215,000 km (135,000 miles), I did not have any oil burning issues with my truck whatsoever. Maybe I was just lucky, maybe it was the obsessive maintenance. But then onwards, the blue smoke at start up and idle made itself as clear as the light of day. I did four ARX treatments, which lessened the blue smoke but never resolved it completely. Being a valve guide issue, and a mechanical one at that, there was no way ARX could have solved this anyway. But I did benefit greatly from the increased compression and fuel economy - which were well worth the treatments alone. At the moment I've got the parts all lined up, waiting for my mechanic to come back from his vacation in late September (wish I was as lucky to take 9 weeks off!). I can get away by just replacing the guides and seals, but I love this truck and plan on keeping it a long time. So I'm replacing a whole lot of stuff in the one go. Prior to the blue smoke, my engine would consume about 250 ml between 5,000 km (3,000 mile) oil changes. Once the blue smoke made an appearance, it was a quart every 2,500 km (1,570 miles). I've tried nearly every mineral and synthetic blend on the market, but the consumption figure never changed. It was always a quart every 1,570 miles. If anyone's interested, here's a list of the oils I tried in this application:
  • Gulf Max 20W-50 SL/CF
  • Agip Super XL 20W-50 SJ/CF
  • Motorcraft Synthetic Blend 10W-30 SM/GF-4
  • Mopar 10W-30 SM
  • ACDelco Select 10W-30/20W-50 SM
  • Mobil Drive Clean 10W-30
  • Castrol GTX 10W-30/20W-50 SL/CF
  • BP Visco 2000 SJ/CF
  • BP Visco 3000 SL/CF
  • Pennzoil LongLife Gold 15W-40 CJ-4/SM
  • Fuchs Titan Universal HDEO 15W-40 CJ-4/SL, A3/B3/E2
  • Q8 T500 20W-50 CF-4/SL, A3/B3/E2
  • Q8 Super 20W-50 SL/CF
  • Morris Multi-Life Competition 10W-50 Full Syn SL/CF, A3/B3
The British Morris 10W-50 was this engine's first full synthetic in the slump. I also thickened the oil with STP Oil Treatment hoping that, combined with a full synthetic, it would help reduce consumption some. It reduced oil consumption, but not really by a significant amount - worked out to about a quart every 3,200 km (2,000 miles) when I did the math at the end. At my last oil change, I went for an oil ExxonMobil supplies to Toyota for their Lexus brand of vehicles. A full synthetic SM rated 5W-40. It's currently the cheapest full synthetic in the market, which was why I chose it. I just wanted to stick with a synthetic, and knowing the engine will burn anything I throw at it, I thought why not? After changing the oil, the engine ran significantly smoother (especially at 4,000+ rpm) and much quieter. My initial thought was it's just psychological, the oil is new...it'll go away soon. The oil has been there for 5,472 km (3,420 miles) now. It still runs as smooth and as quiet as it did when the oil was changed. Now the better bit - I stopped seeing blue smoke in my rearview at start up and extended idle. I don't know if the 90 ml of ARX I add to each oil change worked really well with the Lexus oil, but when I first changed the oil, I would see clouds of blue smoke when I started her up in the morning. I attributed this to the 5W when cold, but now it just disappeared. I had my father start the truck in the morning, to see up close if there was any blue smoke. A faint cloud of blue smoke came up, barely noticeable but you could smell burnt oil. A technician I spoke to at the Lexus dealer told me part of the oil's additive package contains seal swellers, so that would have some part to play as well I would imagine. The best bit - no make up oil was added over the past 3,420 miles at all, and it sits at over the 500 ml mark on the dipstick. Even after the oil burning issue is addressed, this is all this engine (and probably my other vehicles) will ever see, with 3 oz of ARX! \:\!
 
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I had the same engine in my minivan. Oddly the smoking at idle occurred at the same mileage. This engine also fatigued oil at predictable intervals. No consumption for 3k ..then progressive (but untracked) consumption from there out. The oil change was on the 2nd incidence of one quart of consumption. Keep in mind that these were older 5w-30 formulations and this was how the engine reacted to anything beyond 3k OCI's from new. After the smoking event @ 130k, there were notable effects with different oils. Formula Shell ..the cheapest stuff I had ever bought, produced best results. PZ YB, erased all that in a few miles of usage. After Auto-Rx, 90% of the fogging went away unless you idled too long. That is, it had more tolerance for idling. You could sit through a traffic light without producing a massive plume of fog. This was almost a given otherwise.
 

Falcon_LS

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 Originally Posted By: StevieC
Excellent results... Makes me want to try the Lexus brand oil! Bud!
I would definitely recommend trying it. As with any oil, your engine may or may not like it...but nothing ventured, nothing gained. ;\)
 Originally Posted By: duaneb9729
Thank you for sharing your experiences!! Very interesting
You're welcome! Definitely brought a new meaning to "cheap is good". \:\!
 Originally Posted By: Gary Allan
I had the same engine in my minivan. Oddly the smoking at idle occurred at the same mileage. This engine also fatigued oil at predictable intervals. No consumption for 3k ..then progressive (but untracked) consumption from there out. The oil change was on the 2nd incidence of one quart of consumption. Keep in mind that these were older 5w-30 formulations and this was how the engine reacted to anything beyond 3k OCI's from new. After the smoking event @ 130k, there were notable effects with different oils. Formula Shell ..the cheapest stuff I had ever bought, produced best results. PZ YB, erased all that in a few miles of usage. After Auto-Rx, 90% of the fogging went away unless you idled too long. That is, it had more tolerance for idling. You could sit through a traffic light without producing a massive plume of fog. This was almost a given otherwise.
Thanks for sharing this! \:\! A lot of people here spend the money on new valve seals and achieve the same results I got with ARX. I've spoken with many owners of vehicles with this engine, and most just follow what their mechanics recommend - just replace the valve seals. They were telling me to do the same, but I don't see the logic in spending $150 every couple of months on something ARX could also do for a fraction of the price. It's pretty much a situation of the blind leading the blind here. Smoking 3 litre Mitsubishi - just replace the valve seals with genuine parts! To quote a highly respected Mitsubishi Tech I spoke to, "Replacing the valve seals is merely a band aid fix." I have yet to see someone actually replace their valve guides, and even the parts people at the dealership told me they haven't sold any, unless somebody's got a snapped timing belt and is required to replace them. Even then, it's just one or two instead of the whole lot.
 
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I`ve been told that true synthetic oils won`t burn like dino oils,and that used car lots will sometimes fill their oil burners up with synthetic oils so they won`t smoke when a potential customer takes it for a test drive. Is this fact or myth?????????
 
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