Thicker or thiner oil for high rewing V6?

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799
Location
Washington, DC
I have 2000 Mazda 626 with high rewing V6...Aprox 4000 RPM at 80MPH. It redlines at 7000RPM and I like to hit it from time to time. So far I used M1 5W-30, 10W-30 and currently GC 0W-30. I like to run oil for 10K. Recently I started thinking about M1 0W-20. What do you guys think would be PROS or CONS of using this oil in this type of engine? Or should I stay with thicker GC? You can see my two analysis results here : http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=000864 here is more info about engine: Specs - 2.5V6 - 28psi @1000rpm, 49-71psi @3000rpm Also engine architecture(mine is 2.5 V6): Engineering Data Mean Piston Speed - V6 Engines - all-alloy DOHC 24V 60-degree V6 configuration - Split Crankcase - as 911 flat-6 offers increased rigidity over traditional bearing-cap solutions for high-rpm capability (7800rpm 2.0V6) and low NVH (winning 1992 German engine award) - Bearings - 4-bolt Mains, with a further pair of bolts at each bearing section. Key journals & bearings are oversized regarding width. Bearings are triple-layer heavy duty - Crankshaft - Forged, nitrided, triple-lapped, mirror-finished - Piston Squirters - Upper bearing journals contain piston oil-squirters to aid cooling - Exhaust-Valves - Stainless steel & sodium cooled - Pistons - Lightweight to reduce reciprocating mass, piston skirts are moly coated to reduce friction - Head Gaskets - Stainless steel is used, with torque-to-yield bolts - Stroke - Very short stroke creates low crank angles & low rod/bearing loads Engine Dynamic Stress Levels o Mean Piston Speed, MPS - 2.5V6 MPS = 0.167 * 2.92 * 7000 = 3170 ft/min at 7000rpm - 2.0I4 MPS = 0.167 * 3.62 * 6500 = 3929 ft/min at 6500rpm - F1 engine MPS = 4519 ft/min at 16,400rpm - As a benchmark, MPS - under 3,500 ft/min - Good reliability - 3,500-4,000 ft/min - Stressing - over 4,000 ft/min - Very short lived o Bore & Stroke - 2.0 Bore*Stroke of 83x92mm (3.62" long stroke) - 2.5 Bore*Stroke of 84.5x74.2mm (just 2.92" stroke) - For comparison F1 engines have 70x42mm (1.65" stroke) o Ring Loadings Top-rings must balance high-rpm capability and wear, a thin ring allows high-rpm capability, too thin and wear becomes an issue. With reduced crank angles from a short stroke ring wear is reduced. A 1.5mm ring is beneficial over a 1.0mm ring for high-rpm. Maximum-Piston-Acceleration (MPA): 2.5 top-ring - 1.49mm/0.06" - MPA Permitted = 77,000ft/sec^2 - MPA Experienced = 51,354ft/sec^2 at 7000rpm 2.0 top-ring - 1.17mm/0.046" - MPA Permitted = 105,000ft/sec^2 - MPA Experienced = 70,157ft/sec^2 - The BMW M5 in comparison experiences MPA of 90,000ft/sec^2 on a 1.5mm ring. Lighter rings create reduced accelerative forces, reduced ring/piston interface overheating and reduced hammering of the piston-ring-groove. Too light and ring longevity is adversely affected. MPA = (rpm^2 * stroke"/2189)*(1/2A), A = ratio between rod-length-between-centres to stroke. 2.0 rod-centre-dist = 135mm; stroke = 92.0mm; A = 1.47 - MPS-2.0 = (6500^2*3.62/2189)*(1.2*1.47) = 51,354 ft/sec^2 2.5 rod-centre-dist = 138mm; stroke = 74.2mm; A = 1.87 - MPS-2.5 = (7500^2*2.92/2189)*(1.2*1.87) = 70,157 ft/sec^2 Both the 2.5V6 & 2.0I4 engines are engineered for longevity. The 2.5 engine is likely to be the longer lived engine subject to identical maintenance to the 2.0 engine. Mazda V6 engines are assembled entirely by robots, not humans, at the Osaka engine plant in Japan alongside Rotary engines. Ford bench testing, with very minor changes, showed the V6 to be capable of continuous running at 8900rpm - well beyond redline 7500rpm. SAE paper "SAE920677" covers detailed design of the engine.
 

MolaKule

Staff member
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21,957
Location
Iowegia - USA
quote:
Piston Squirters - Upper bearing journals contain piston oil-squirters to aid cooling
One additional comment. I have noticed that engines with oil squirters and small sumps really stress the oil. Nissan has this design as well. Do UOA's and look at the wear trending. I never recommend longer drain intervals without doing UOA's.
 

zoomzoom

Thread starter
Messages
799
Location
Washington, DC
Looking at the link you gave me it seams that difference in wear would be rather small between 30wt and 40 wt. Would that hold true for 20wt? As I see it 20wt would flow better therefore keep engine cooler and better oiled at high RPM. Does this statement makes sense?
 

MolaKule

Staff member
Messages
21,957
Location
Iowegia - USA
I would still stick with the 30 weights unless you're in an extremely cold environment. The 30 weight will still probably shear down to near a 20 weight under high-heat, high loading conditions.
 
Messages
254
Location
Calgary AB
I had a car with that excellent 2.5L V6 too. I loved that engine! Reved so freely and made good power. I actually drove it (Probe GT) across the country in 3 and a half days (Vancouver to Montreal thru the States I90 and I92) Going through Montana I wasn't below 100mph very often and often much faster. I had check engine light in Montana but just kept going, it had to be the emissions system right? [Smile] Anyway I sold that car with 180 000km on it and it is still going strong to this day, driven by a young lunatic. I used synthetics all types (Castrol, Pennzoil, Mobil) and grades 5w30 to 5w50.
 

MolaKule

Staff member
Messages
21,957
Location
Iowegia - USA
The newer V6's in general are really smooth and have higher power densities than did those engines of "yore." I really like the 3.5 L V6 in our Pathfinder. Plenty of power and it revs so smoothly.
 

Patman

Staff member
Messages
22,012
Location
Guelph, Ontario
quote:
Originally posted by sub_zero: I had a car with that excellent 2.5L V6 too. I loved that engine! Reved so freely and made good power. I actually drove it (Probe GT) across the country in 3 and a half days Anyway I sold that car with 180 000km on it and it is still going strong to this day, driven by a young lunatic. I used synthetics all types (Castrol, Pennzoil, Mobil) and grades 5w30 to 5w50.
My mom's 94 Probe GT has just over 219,200km on it now, she's owned it since new and for most of it's life I've changed her oil with Mobil 1 10w30 in 8000km intervals. That engine is definitely sweet! I also agree with MolaKule, the Nissan 3.5L V6 is also very nice, my dad had that engine in his last vehicle, a 2001 Infiniti QX4. He changed the oil every 10-12,000km, always with Mobil 1 (10w30 in summer, 5w30 in winter). He only had it for three years though, so he only had just over 100,000km on it when the lease was up.
 

Patman

Staff member
Messages
22,012
Location
Guelph, Ontario
quote:
Originally posted by geeeman: But, Patman, why M1 in a leased vehicle???
My dad has leased vehicles ever since 1985, and always gets 3 year leases too. He simply preferred to use M1 so that he could go with longer intervals, and for easier winter starting too. He would rather get the oil changes done every 10-12,000km instead of every 5000km. And he treats every car as if it is one he plans on buying at the end of the lease, just in case he ever decided to buy the vehicle for my mom (which he never ended up doing but came close a couple of times) With his new vehicle, a 2004 Volvo XC70, he is not leasing it, but he financed it over 4 years. That's because he's retiring in a couple of years, so he'll no longer have the car allowance which paid for all those leased vehicles in the past, and this one will be kept for a much longer time period. He's going to be doing 12,000km intervals with this car, and he's running GC 0w30 right now in it.
 
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