Power loss with Heavier Oils

[mf150]

Hi- My mechanic put 15W50 Mobil 1 in a truck designed for 5W-30/10W30 and we noticed a big difference at acceleration. We changed it back to 10W-30 that same day.

 

[sprintman]

Fuel economy is way down on my Outback that has 5W30 dino in currently compared to Redline 5W30 or Delvac 1 5W40 run previously. Good job Pennzoil has healthy moly dose as its probably getting well used.

 

[MNgopher]

According to the EPA (cringe), using a base of a 10w40 oil, the following oil grades offer fuel economy gains of approximately (and these are maximum allowed): 10w30: 2.0% 5w30: 3.4% 5w20: 4.2% I'm sure that somewhat relates to horsepower, but not in a totally straightforward manner. Also does not consider extra wear. I've heard all the stories that 5w30 is bad and don't run it unless you live in the arctic. I've been using 5w30 since 1989, and never had a problem with it, even when living in the Southwest for 5 years, and believe it or not, we do have summer an 90+ degrees here too. I think a big part of the thinner grades here is that consumers are used to it, where they are not in other parts of the world, and as a result, availibility is not very good.

 

[Schmoe]

quote:

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Originally posted by csandste: I can see a slight drop off in MPG going from 5W30 to 10W30 although I prefer the latter.

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Say what????? I thought it would be more related to the higher temperature number as opposed to the winter number. I mean, once the engine warms up, in this case, it would all be a 30 weight, or not thin out more than a 30 weight.

 

[Patman]

Another problem is that the same engine running the same oil might feel quicker at one part of the day compared to another, and weather plays a HUGE factor in horsepower output too. When it's 50F outside and 30% humidity you're going to make way more horsepower than when it's 95F with 60% humidity. My car's elapsed time in the quarter mile changes drastically between those two points (it goes from 13.74 at 100mph to about 14.1 at 96 mph from cold to hot) Also with my car, I notice the engine feels stronger down low if I'm stuck in traffic for a while and the coolant temps are up around 230. I know the opposite should happen here though, and if I then go full throttle, the engine does not feel as strong up top as it does during times when the coolant temp is below 200F again. So basically what I'm trying to say is that you shouldn't always judge how a car "feels" and think it has everything to do with a change of the oil.

 

[Dr. T]

It is brand specific. I will attest that I too put in M-1 15-50 (going from 5-30) and power was waaaaay down. The Syntec 5-50 (as moribundman pointed out) was a totally different animal. I too found it better than either the 0-40 or 15-50 with respect to fuel economy and consumption. Some power loss is misleading. If an engine is run on a steady diet of 5-30 for eg., power will be way down because of too much crap in the engine. Recommendation: use auto-rx first. Also, power delivery will be smoother, less abrupt and skittish. New engines aside, if blowby is occuring, power if being wasted. You will gain more power by using a grade with less blowby as the engine will be "sealed" better. This is why I hate consumption.

 

[Sin City]

I believe the condition of the motor will also play a big part in the motor oil viscosity requirement. I noticed my mothers old Geo Prism had started to use oil when it had about 146,000 miles. When I changed the Valvoline SynPower 5W-40 to Castrol Syntec 5W-50 the motor was MUCH quieter when it was first started. It takes less time to build oil pressure. The car does not have enough miles yet since its last oil change to measure oil consumption. Since the motor is so much quieter I would think that it is also wearing less. I rarely drove this car in the past so I can't be totally sure but I do not detect any loss of power or performance. If I can put enough miles on this car in the next six months or so I will do a UOA and post it. This is now my spare car and I am driving this old car only so I can get a UOA on Castrol Syntec 5W-50. I have seen three UOA's on Syntec 5W-50 that all looked good but everyone seems to love to hate this oil (Syntec 5W-50). For anyone not living in the USA the Geo brand was an idea that General Motors had to sell foreign designed or built cars in the USA at Chevrolet dealers. The Geo Prism is nearly identical to the Toyota Corolla. They gave up on this idea and the last few years the Prism was sold as a Chevrolet and the Geo brand was put to rest. [ July 19, 2003, 12:57 AM: Message edited by: Sin City ]

 

[moribundman]

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The Geo Prism is nearly identical to the Toyota Corolla

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Interestingly enough, the Geo Metro, gas saver par excellence, was practically the same as a Suzuki Swift. It was built under license, and I'm pretty sure the 3 cylinder engine was also available in the US. PS: I have ambivalent feelings towards Syntec 5W-50. On the one hand I used it for a long time and did like that oil, on the other hand I don't like the Castrol labeling and pricing policy.

 

[Patman]

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Since the motor is so much quieter I would think that it is also wearing less

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Common misconception, but no, it's probably not the case. The thicker oil absorbs more of the sounds, so it makes the engine quieter, but more than likely you're getting higher engine wear numbers. If an oil is too thick for the application you end up with higher oil temps and less than optimal oil flow.