Hello there everybody, I found myself amazed reading a bunch of oil threads in this forum during the last weeks and I'm grateful as I've read lots of good advices and researches that really helped increasing my awareness in the matter.
I'm a European (from Rome,Italy) owner of a MY17-> Toyota GT86 (brz/frs) and I would really like to ask this community a bunch of questions regarding the best oil for this Subaru engine according to my driving needs.
But first let me do a quick recap/summary of what we know about this engine for now.1- What the manual(s) say Europe:
0w20 is the reccomended oil, you can put 5w30 if you cannot find 0w20 but you have to put back the 0w20 at the next change. API SN. A thicker oil can be used in case of high speeds / extreme load usage. Japanese Manual:
SUBARU MOTOR OIL ECO 0W-20, SUBARU MOTOR OIL SN 0W-20 SUBARU レ・プレイアード ZERO 0W-30, SUBARU MOTOR OIL ECO 5W-30, SUBARU MOTOR OIL SN 5W-30 SUBARU Castrol SLX Professional SM 5W-40The officine manual
says that you're good if within an 80° C oil temp you reach a pressure of >= 0,5 bar (7,2 psi) idling or >=5,03 bar (7250 psi) at 6000 rpm and does not give any other scenario than this.2- What failure history say
It seems that a number of bearing rod failures
had happened in the 2012/2013 launch models, doesn't seem connected (just speculating) to the oil in use or to a design flaw, since there has not been any official recall
by Subaru and Toyota enforcing users to change rod bearings or the oil used. The only recall for this engine seems to regard the valve springs until MY2015
There's also a number of engine failures encountered during track usage regardless of the oil weight, most likely to the great G-Forces generated by the usage of semislicks or grippier tyre than UHP or Street tyers and the boxer's design. In reality there's also a number of MY17+ that had rod bearing failure, the last one (in Italy) a couple of weeks ago during a track day on the out-lap, with Bardhal 5W40, at 20k km (approx 12,5k miles) although the owner said that he had driven the car in several trackdays before with 0w20 oil inside but always with an upgraded oil pan and oil cooler. So who knows why do the rod bearing fail in this car? In italy there's a total of less than 2000 GT86/BRZ sold and so far it looks like we had 20 failures for what we can know on the web, some of the in track, some of them had never been abused by their owners.3- What the web saysOil pressure panic:
A bunch of people are concerned about the oil pressure drop at higher temps. The car does not have neither an oil radiator cooler nor a water/oil heat exchanger, the temps can go up really fast to 120/130 °C (248/266 F) if you go WOT for a few minutes. The original ECU
is programmed to change behaviour if oil reaches a temperature of 125° C (ca. 255 F) and starts cutting hp.UOA:
most of them are on 5W30 oil (good ones), and some people claim to get good UOAs of 0w20 trackday samples regarding wear, but now showing results. In Europe we don't have a culture for UOA, I would like to try something like that for my car with the next oil change but the prices go from 100 to 250 € per sample wich I find rather expensive, how much do they cost in North America?Car enthusiasts
say that the 0w20 is a gift to Greta Thunberg and an oil created only to aid car manufacturers to reach CO2 emissions limit standards in europe, and it's not good for a sports car like ours.Friends with Gt86 say
that I'm a fool to use 0w20 grade, but here we do seem to have Dr. Haas happy with 5w20 on Ferrari, Lambo etc.4-What I learned in this forum so farHTHS
it seems by a presentation of Boris Zhmud dated 2016 that low hths oils are good for fuel economy just at high speeds and low load scenarios, while they perform less than higher viscosity oils in low rpms (below 1500) and high load scenarios. He points that a safe HTHS value for good wear protection starts from 2,85+, that low hths and i think ILSAC G5+ oils tend to have an higher additive arsenal to reduce boundary lubrication. He states also that the fuel savings in a 30k km/year is really too small to compromise the potential loss in wear protection.Engine Wear
From some case studies
seems like 95% of the wear in the cylinder bore comes within the first 20 minutes of usage, maybe due to an improper oil film distribuition or non-optimal oil temperature while the piston ring wear seems to be connected to the brake mean effective pressure (BMEP).
of course when the engine is at nominal functioning condition the wear goes up with enigne rpms but non in a proportional manner. Cavitation
may be another factor to take into account when selecting the right oil5-My struggles in finding the right oil
This is the section where I call out for Your help.
The Gt86 is my daily/commuting/weekend and trackday
- I live in Rome
, winter temps 0-15° C, summer temps 22-39 °C
- I live near the highway
, so every time i start up i'm on the highway cruising at 2500 rpms with the both the engine and oil in non-optimal and cold condition for 20 km, then 3 km in the city traffic.
- I am in WOT condition everyday in the last 8km (on 52 driven in total)
of the travel back to home (with both engine and oil in normal temperatures)
- I plan to track the car 2-3 times a year, mostly in autumn/spring in slow tracks that are 2nd and 3rd gear and 130 km/h max speed with tight curves and a very short straight, and I do some spirited driving 5 to 10 times a year, usually not pushing the 7200 rpm redline since the torque is finished at 6500/6800 with the 95 ron fuel.
- car must stay stock for the next 2,5 years so whitin the offiicial maintenance schedule I have to stick with either the 0w20 or 5w30 by Toyota (should be Motul).
For now I've driven 4600 miles with the stock 0w20 inside, then drained it and switched to a 5w30 Motul 8100 eco-lite (hths 3.3) since it was May and i did track the ca. I kept the oil for the whole summer then switched back to the mandatory 0w20 Toyota with the first service at 8900 miles (so 4300 miles later). I have to report that since the first kilometer with the 5w30 the car felt really slower in gaining momentum, and it felt like reborn when a lower viscosity oil was back in the engine. Man i really hate the 5w30 performance-wise
and for the tipical usage that i do (80% commuting) I also was scared thinking that I might have been sacrificing the cold engine usage that I happen to experience everyday.
So here we go with the final question(s)
Taking into account my driving habit, the kind of climate, the car and the history of failures:
- Are those rod bearing failures random?
- Should I be more focused on protecting the car from the high load wear (WOT) or should i focus more on the cold start / normal usage?-
- Should I keep the habit of changing oil weight or it's best to stick to one weight only?
- Should I choose a compromise hths (lower than 3.3 but higher than 2.85 to ensure wear protection) like a 0w30 oil (2.9/3.0)?
- Should I stick to ILSAC G5 oils for the boundary friction protection?
- What should I do to try and get the longest life possible out of this car?
- What da ***k is the right oil for this car?
- When the warranty will have expired, would a water/oil exchanger more suitable than an oil cooler?
- Could the installation of Billet Power Blocks (to shift the torque curve to lower rpms sacrifing the total hp at the rev-limit) prevent some wear (since I rev less) or the major torque on the lower end would cause more load and wear at the rod bearings?
Thanks in advance for the answers!