Better MPG with thicker oil...

Messages
11,284
Location
Spring HIll
I'm going to swim against the stream here. I had M1 SM 5w-20 in my Saturn (96 DOHC model, 125K) and drained it . MPG was 32-35MPG in my daily commute which is almost all highway miles at 65-70MPH. Performed a "poor man's flush" with PZ dino, then filled the crankcase with Pennzoil HM 10w-40 with LC. MPG is 32-36. Yes, MPG is the same or HIGHER. I'm in disbelief myself as my driving style nor gas type has changed as I used the same station and grade for this test. Shell 87 with FP. I was hoping M1 SM 5w-20 would hit near the coveted 40MPG mark. I'm still amazed that a thicker non-PAO gives good MPG as the lighter weights do. Comments, thoughts?
 
Messages
7,077
Location
Ontario, Canada
I noticed a similar thing in my Subaru. Redline 5w20 gave me slightly lower, or the same gas mileage as the 0w20/0w30 mix I had in the previous winter, and low-end torque was slightly reduced. Maybe the rings aren't able to seal well enough with thin oil. The very best gas mileage I've ever had was when I put in some Pennzoil 5w30 SM while I was in the US last fall. The SM's are just beginning to show up in Canada, and I think they will make a difference. Maybe for some engines, a cheap oil with higher viscosity and lower HTHS would seal the rings well, and reduce friction at the same time. I've tried 15w40 in this car, and gas mileage was down by 2-3% at 63 mph. [ March 26, 2005, 11:10 AM: Message edited by: oilyriser ]
 
Messages
39,805
Location
Pottstown, PA
obscure possibility: Did the engine evidence more blow-by with the 5w-20? At those speeds, I would imagine and aside from flogging accelleration, you're at the highest constant level of cylinder pressure. Perhaps you've got better ring seal. Consumption?? Just a thought... [I dont know]
 
Messages
36,438
Location
ME
I get best SOHC Saturn MPG with Pennzoil LL 15w40. I've got some more of that, and some Motorcraft and Supertech (ugh) 15w40 that I'll be comparing to the Pennzoil. It is also the summer weather and gas. I will be changing both cars to 15w40 soon and will report results. Low end torque and driveability get better too. Passenger car 10w40s, Chevron Supreme and Superflo, don't do quite as well; I think because they shear down.
 
Messages
4,643
Location
The Garden State
It's interesting that you get fewer mpg with a lower viscosity oil. I have a 1996 Ford Contour with the 4 cyl 2.0L Zetec that recommends 5W-30. In my pre BITOG days I always thought that "thickerer is betterer". So I used Castrol Syntec and Quaker State synthetic 5W-50. Needless to to say my mpg and seat of the pants feel went to he*l with those oils. Went back to using Mobil 1 5W-30 and then Schaeffer's Supreme 5W-30 Blend and my mpg increased tremendously and the "seat of the pants" feel was much better. I honestly don't see how a thicker than recommended oil will help your mpg or engine wear for that matter unless your engine is "very loose". But then you have bigger long term problems to contend with. Whimsey
 
Messages
43,660
Location
'Stralia
quote:
Originally posted by Gary Allan: obscure possibility: Did the engine evidence more blow-by with the 5w-20? At those speeds, I would imagine and aside from flogging accelleration, you're at the highest constant level of cylinder pressure. Perhaps you've got better ring seal.
Only thing that I can think of, other than loss of hydrodynamic lubrication (which I don't beleive)
 
Messages
546
Last year I reported the increased MPG after switching from 5/10W-30 Schaeffer's Blend to the 15W-40 Schaeffer's Blend. It's a 99 Nissan Sentra, 1.6L engine, auto-transm. I had never gotten over 32 MPG before the switch. I made the switch and started on a 6,020 mile trip and acquired an overall 34.95 MPG throughout. I have also recently noticed I'm getting 32 MPG driving around town here. To be fair, I must also include that I began using Fuel Power at the time of the switch to the 15W-40 and that might have also been a factor. Anyway, my engine didn't blow up and is saving me fuel still. I now have Schaeffer's 9000 5W-40 on order but delivery has been delayed.
 
Messages
4,378
Location
Camas, WA
Piston rings seem to be the biggest single contributor to engine friction, 30% or so. It appears that there is mixed lubrication at the ends of the stroke, where a heavier oil might help. Engines with large valvetrain friction might see better results with heavier oils too. http://tools.ecn.purdue.edu/ME/FacResPP/Sadeghi_KrousgrillME%20Research.pdf Friction at the piston ring cylinder liner (PRCL) interface accounts for approximately 30% of total engine friction. The objective of this research is to experimentally investigate the fundamental lubrication phenomenon at the PRCLinterface and evaluate the effects that surface modifications have on the friction. A test rig was designed and constructed to reciprocate an OEM or modified cylinder liner segment under a stationary OEM or modified piston ring segment with a known normal force, lubricant, and RPM. The ring is connected to a piezo-electric force sensor tomeasure the friction force. Dimples approximately 100 µm in diameter by 5 µm deep were laser micro-machined into the surface of the piston ring to reduce friction near the ends of stroke where mixed lubrication occurs. Significantreductions in friction have been measured for the modified surfaces, and agreement with numeric simulations of the OEM case has been demonstrated. http://www.vtt.fi/inf/pdf/tiedotteet/2002/T2178.pdf As presented by Coy in his qualitative wear transition model, conditions of hydrodynamic lubrication at the mid-stroke region of the piston motion give rise to full film lubrication (λ > 5) and zero wear, while sliding under less favourable conditions in the vicinity of the dead centres of the piston motion cause mixed lubrication (λ = 1...5) and wear inversely proportional to the oil film thickness (Coy, 1998). The effect of the oil viscosity on the frictional behaviour of piston rings has been investigated by Durga and co-workers (Durga et al., 1998). The oil viscosity affects friction values under conditions of pure hydrodynamic lubrication when the rings are fully flooded. Higher friction values occur at higher viscosity. Suggestions are made that a slight increase in friction, which is observed at mid-stroke of the piston motion, could be partially caused by high-speed shear. The rings experience a very high contact pressure at mid-stroke, which could lead to oil starvation and thus friction increase. Works by several authors, using test rigs and motored engines, show that a thicker oil film can be reached by increasing the engine speed or the oil viscosity, or by the decrease of the load (cylinder pressure) or temperature. However, results that do not completely follow the trends expected from the theory have been published. The degree of the influence of these factors is different and their interaction in a firing engine has an important impact on the lubricating oil film thickness. (Richardson and Borman, 1992, Dearlove and Cheng, 1995, Shenghua et al., 1996, Harigaya et al., 2000).
 

ToyotaNSaturn

Thread starter
Messages
11,284
Location
Spring HIll
quote:
Originally posted by Triple_Se7en: You said your mileage increased 1 MPG?????? Warmer weather????????
Perhaps, but the 5w-20 was in for some warm weather and no prolonged starts. I've even reduced my speed from 75+MPH to 65-70MPH...usually 68MPH just to achieve a "higher" MPG with the 20wt oil.
 
Messages
1,183
Location
Vermont
With what information that's given, this definitly feels like a shot in the dark. Perhaps with the 20w at operating temperature, the hydrodynamic lubrication reg. was being breached, causing an increase in friction. A used oil analysis may show increases in lead if this was to include bearing surfaces, from what I have gathered from other people's opinions here on the board. The point about excess blow-by with a 20w at operating temperature is another possibility, but how might this be checked? Could a compression/leakdown test be performed on a hot engine? I understand that pressure in the cylinders obviously reach higher values and thus a greater percentage of bleed-off of what's seen by simply cranking the engine over will occur, and then you have the localized hotspot situation that further thins the lubrication oil in that area. This sounds to complicated to test, but perhaps others could come up some theoretical values based upon hard data. Cooller engine temperatures may yield better mpg performance, due to viscosity characteristics that mirror a heavier weight oil that is operating at a warmer temperature. This I feel would go to explain the mileage differences seen when going from 5w-20/30 to a 15w-40 in the same engine. I can't help to think of potential differences in the designs of engines where these viscosities are recommended and regularly used. There are also the differences that HTHS values may play, but I'm not sure how to go about that possibility. I also here that not all if only a few 15w-40 oils (diesel lube) contain friction modifiers, thus further effecting mileage results as it is hinted, in an engine that may not often see barrier lubrication conditions. Perhaps the 5w-20 recommendation is further backed by a general consensus that that majority of motor vehicles are used for short distance commutes (thus never really reaching or sustaining full operating temps for long). Perhaps there's more to the question that appears on the back of my insurance bill that asks how many miles are driven in a week, to school, work, or other. Being that I don't work for any of the administrations that are webed together in the whole transportation infrastructure, I again don't know of any such facts. Interesting findings guys.
 

ToyotaNSaturn

Thread starter
Messages
11,284
Location
Spring HIll
Lots of interesting thoughts! There's no consumption whatsoever. I'm fortunate to have one of those Saturns that doesn't consume oil. Does blow-by = consumption?
 
Messages
74
Location
Michigan
quote:
Originally posted by ToyotaNSaturn: I'm going to swim against the stream here. I had M1 SM 5w-20 in my Saturn (96 DOHC model, 125K) and drained it . MPG was 32-35MPG in my daily commute which is almost all highway miles at 65-70MPH. Performed a "poor man's flush" with PZ dino, then filled the crankcase with Pennzoil HM 10w-40 with LC. MPG is 32-36. Yes, MPG is the same or HIGHER. I'm in disbelief myself as my driving style nor gas type has changed as I used the same station and grade for this test. Shell 87 with FP. I was hoping M1 SM 5w-20 would hit near the coveted 40MPG mark. I'm still amazed that a thicker non-PAO gives good MPG as the lighter weights do. Comments, thoughts?
1 MPG is hardly anything to be concerned about. I would attribute it to other factors...different gas,tire pressure, ambient temperature...etc. Thicker oil just increases parisitic drag. Just doesn't make sence to me.
 
Messages
5,785
Location
Dixie
You have worn piston rings and cylinder walls and the thicker oil is giving you a better ring seal and higher compression....This is related to the post by 1sttruck. The # of miles on this engine - and the fact it's a Saturn - are the keys in this case.... TS
 

ToyotaNSaturn

Thread starter
Messages
11,284
Location
Spring HIll
Just filled up on the way home tonight, another 36MPG tankfull. I've tried long and hard to achieve this type of MPG, looks like I've stumbled upon the solution. Tooslick, I believe you're right. I'm thinking that would explain why high insolubles and fuel dilution is always an issue with this car... If the cylinder walls/rings are worn, would consumption necessarily be an issue? I never see the level on the dipstick move.
 

ToyotaNSaturn

Thread starter
Messages
11,284
Location
Spring HIll
The PZ HM oil simply amazes me! Just filled up again, 34.0 MPG with the A/C on and lots of city driving on the last tank. 87 Shell with FP. No V-Power whatsoever. I'm sold on PZ HM in this car! [Happy] [Happy] [Happy]
 
Top