10W-40 and Energy Conserving, GF-5 and SN rating

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I am running 10W-40 conventional oil in my car. I know that by definition it cannot be "Energy Consering" or hold the "GF-5" rating because it is a 10W-40. I am environmentally minded and wondered what the impact was of not running something Energy Conserving or GF-5 rated. My oil is "SN" rated though, and I think I heard that SN and GF-5 have the phosphorus standards (Same Zinc too?) Any help would be appreciated. Thanks, Drew
 
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10w40 by API definition is not Energy Conserving because it is the baseline grade by which Xw20's and Xw30's are rated to demonstrate fuel-saving ability. The minimum fuel economy difference required between a 10w40 and Xw20 oil to get the Energy Conserving endorsement on API standard tests is 2.6% when the oil is fresh and 1.2% after 100 hours of aging. Fuel economy improvements from 5w30 and 10w30 grades are less than that. So if you were to switch your engine over from 10w40 to Xw20 oil, you could expect at least a 2.6% fuel economy improvement if you could drive consistently enough and measure fuel consumption accurately enough to detect a difference. Then you could expect the improvement in fuel economy to lessen over the next 5000 miles. So if your car gets 20mpg, it could go to 20.5mpg with the 20-weight oil. This is assuming your car is designed to run on 20-weight.
 

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1% fuel economy perhaps.... Probably less practically speaking. Tiny in terms of your use, but huge in terms of 100 million cars on the road doing 10k miles a year. Does your application require GF-5? Maybe not. If not, would it be beneficial? Sure. There are places that state the differences in performance between GF-4 and 5 in terms of cleanliness and other metrics. 40wt oils are allowed to havea bit more ZDDP than 30 wt oils, FWIW. If youre not burning, it doesnt matter much, IMO.
 
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Originally Posted By: soundwavefd
I am running 10W-40 conventional oil in my car. I know that by definition it cannot be "Energy Consering" or hold the "GF-5" rating because it is a 10W-40. I am environmentally minded and wondered what the impact was of not running something Energy Conserving or GF-5 rated. My oil is "SN" rated though, and I think I heard that SN and GF-5 have the phosphorus standards (Same Zinc too?) Any help would be appreciated. Thanks, Drew
I think you are asking the wrong question. If you tell them what your engine is and what your operating conditions are, people here will help you choose the right oil. 10W-40 is a somewhat antiquated grade and these days it's mostly used to control excessive oil consumption.
 

soundwavefd

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I have a 1993 Mazda RX-7 and have heard that 10W-40 would be a good oil grade to use (10W-30 would be ok as well). I just wanted to know about those environmental issues I had.
 

soundwavefd

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Am I right that the phosphorus standards of GF-5 AND SN oils are the same (Phosphorus limited to 800 ppm and Zinc is not limited for either) So that even if I am using a 10W-40 that is "SN" rated it will have the same limits on ZDDP as other lower weight oils?
 
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Originally Posted By: soundwavefd
I have a 1993 Mazda RX-7 and have heard that 10W-40 would be a good oil grade to use (10W-30 would be ok as well). I just wanted to know about those environmental issues I had.
To be fair, and the regular readers here will be shocked with me saying this, 10w-40 is probably a good choice for your application. It is also important to note that not all 10w-40 grades will have substantially more Zn or P than their GF-5 counterparts. They may be allowed to have more; that does not mean they will.
 
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Originally Posted By: soundwavefd
I have a 1993 Mazda RX-7 and have heard that 10W-40 would be a good oil grade to use (10W-30 would be ok as well). I just wanted to know about those environmental issues I had.
Well, for best fuel economy and low-range horsepower, you should use the thinnest grade recommended for your engine or the thinnest grade that works. Fuel savings can be substantial from 10W-30 to 10W-40. I saw close to 10% fuel savings myself from 15W-40 (which is thicker than 10W-40) to 0W-20 for light driving. If you are heavy on the pedal, the benefits could easily zero out. You can go slightly lighter with a full synthetic, as a full synthetic doesn't excessively shear like dino does, but apparently they are not recommended for rotary engines. I would get the opinions of the folks here who have experience with this engine on what oil is best to use. If 10W-30 works for you, it's a better choice than 10W-40. Don't worry about ZDDP. It's about protecting the catalyst (not the environment) but for your 1993 engine, it won't make a difference what you use, as your emissions are probably already worn and they are not highly sensitive to begin with anyway. Even with modern engines, the concerns are overblown, as hardly much P actually goes into the exhaust.
 
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Originally Posted By: soundwavefd
I have a 1993 Mazda RX-7 and have heard that 10W-40 would be a good oil grade to use (10W-30 would be ok as well). I just wanted to know about those environmental issues I had.
A quick google search seems to show most Rx7 owners are running a 10w30 oil. either should work
 
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Originally Posted By: soundwavefd
Am I right that the phosphorus standards of GF-5 AND SN oils are the same (Phosphorus limited to 800 ppm and Zinc is not limited for either) So that even if I am using a 10W-40 that is "SN" rated it will have the same limits on ZDDP as other lower weight oils?
No, this is not correct. Study the PDF API brochure at the link below for the actual numbers in the SN and GF-5 specs and the difference between the two as well as the difference in specs for various SAE viscosity grades, diesel-multispec exceptions, etc. http://www.infineum.com/Pages/ACEAandAPITables.aspx
 

soundwavefd

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Good catch! I read that there is not maximum phosphorus level set for SN non GF-5 grades. Thanks!
Originally Posted By: Gokhan
Originally Posted By: soundwavefd
Am I right that the phosphorus standards of GF-5 AND SN oils are the same (Phosphorus limited to 800 ppm and Zinc is not limited for either) So that even if I am using a 10W-40 that is "SN" rated it will have the same limits on ZDDP as other lower weight oils?
No, this is not correct. Study the PDF API brochure at the link below for the actual numbers in the SN and GF-5 specs and the difference between the two as well as the difference in specs for various SAE viscosity grades, diesel-multispec exceptions, etc. http://www.infineum.com/Pages/ACEAandAPITables.aspx
 
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Originally Posted By: Garak
Originally Posted By: soundwavefd
I have a 1993 Mazda RX-7 and have heard that 10W-40 would be a good oil grade to use (10W-30 would be ok as well). I just wanted to know about those environmental issues I had.
To be fair, and the regular readers here will be shocked with me saying this, 10w-40 is probably a good choice for your application. It is also important to note that not all 10w-40 grades will have substantially more Zn or P than their GF-5 counterparts. They may be allowed to have more; that does not mean they will.
I think M1 and Defy are the only 10w40 PCMO's with higher zinc levels, IIRC.
 
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My friend had a 93 TT RX-7 and always used a dino 40 weight. You definitely don't want an energy conserving oil,it's a twin turbo high performance engine.
 
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Originally Posted By: 3311
I think M1 and Defy are the only 10w40 PCMO's with higher zinc levels, IIRC.
There might be a couple others, but it's important to note that just because an oil isn't GF-4 or GF-5 doesn't mean it's going to have elevated ZDDP levels. Some will, some won't, and there's no reliable way of "just knowing," so something like Defy is a good option.
 
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If you run HDEO, available in grades HD30, 10w-30, 15w-40, you can extend oil change intervals. That is one environmentally minded tactic.
 
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I understand that there is a concern that since these rotary engines normally burn oil in order to function and the synthetic oil doesn't burn as well as dino oil (both of which are true), it's recommended to use dino in this engine. Perhaps any 10W-30 dino should do well then. You could also use 10W-40 dino but it will leave more viscosity-index-improver-polymer deposits behind, although the consumption will be less; so, maybe it's overall a better thing. I would say if the consumption is not excessive with 10W-30, use 10W-30. 15W-40 HDEOs are a different story -- they leave behind different kinds of antiwear layers -- not necessarily a bad thing but not necessarily a good thing either, especially if you change back and forth between HDEO and PCMO. Also, 15W-40 is rather thick and you may see some sluggish performance and relatively poor fuel economy. 10W-30 dino oils of today almost don't shear at all and they would probably be equivalent of 10W-40 dino oils of 1980s after they sheared.
 
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Originally Posted By: Gokhan
I understand that there is a concern that since these rotary engines normally burn oil in order to function and the synthetic oil doesn't burn as well as dino oil (both of which are true), it's recommended to use dino in this engine. Perhaps any 10W-30 dino should do well then. You could also use 10W-40 dino but it will leave more viscosity-index-improver-polymer deposits behind, although the consumption will be less; so, maybe it's overall a better thing. I would say if the consumption is not excessive with 10W-30, use 10W-30. 15W-40 HDEOs are a different story -- they leave behind different kinds of antiwear layers -- not necessarily a bad thing but not necessarily a good thing either, especially if you change back and forth between HDEO and PCMO. Also, 15W-40 is rather thick and you may see some sluggish performance and relatively poor fuel economy. 10W-30 dino oils of today almost don't shear at all and they would probably be equivalent of 10W-40 oils of 1980s after they sheared.
So back to the 15W-40 again... do these oils leave VII deposits or much more of other types of deposits? In your experience are these deposits mainly generated during much extended drain intervals or even during shorter drain intervals ? And will these 15W-40 oils cause the sluggishness and poor fuel economy due to original viscosity being thicker, OR due to the deposits they leave in engines? Thanks!
 
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Originally Posted By: fpracha
Originally Posted By: Gokhan
I understand that there is a concern that since these rotary engines normally burn oil in order to function and the synthetic oil doesn't burn as well as dino oil (both of which are true), it's recommended to use dino in this engine. Perhaps any 10W-30 dino should do well then. You could also use 10W-40 dino but it will leave more viscosity-index-improver-polymer deposits behind, although the consumption will be less; so, maybe it's overall a better thing. I would say if the consumption is not excessive with 10W-30, use 10W-30. 15W-40 HDEOs are a different story -- they leave behind different kinds of antiwear layers -- not necessarily a bad thing but not necessarily a good thing either, especially if you change back and forth between HDEO and PCMO. Also, 15W-40 is rather thick and you may see some sluggish performance and relatively poor fuel economy. 10W-30 dino oils of today almost don't shear at all and they would probably be equivalent of 10W-40 oils of 1980s after they sheared.
So back to the 15W-40 again... do these oils leave VII deposits or much more of other types of deposits? In your experience are these deposits mainly generated during much extended drain intervals or even during shorter drain intervals ? And will these 15W-40 oils cause the sluggishness and poor fuel economy due to original viscosity being thicker, OR due to the deposits they leave in engines? Thanks!
Sluggishness and loss of fuel economy is due to the higher HTHS viscosity, which is what mostly determines the oil-caused engine friction. 15W-40 has an HTHS viscosity typically around 4.3 cP, whereas 10W-30 has an HTHS viscosity typically around 3.1 cP. I was mainly talking about the antiwear layers, as HDEOs tend to use somewhat different formulations of ZDDP than PCMO, and these layers will be somewhat different. As far as engine deposits are concerned, I never had a big problem with them when I did use 15W-40 for a long period (six years or so). I think with thicker oil, it's a little bit harder for the oil to flow and therefore it's a little bit easier for the deposits to form. But then thinner oil has a higher NOACK volatility, which may increase the tendency to leave behind some oil-related deposits. VII deposits depend on the type of oil used. 10W-40 has more VII than 10W-40 and it also has more VIIs than 15W-40. Therefore, as for as VII deposits are concerns, which could lead to sludge, I would most worry about 10W-40. In fact, I believe GM explicitly recommended against 10W-40 in the early days precisely for this reason. But then dino 5W-30 also has a lot of VIIs, and it could also be more sludge-prone. With synthetic oil, deposits could only be a worry in turbocharged engines. Coming back to my experience, switching from 15W-40 HDEO to first 5W-20 dino and then 0W-20 synthetic, I am seeing the best performance with the 0W-20 synthetic. I think the thinner synthetic has really cleaned the engine and it's also giving better performance due to lower HTHS viscosity. The engine is certainly running smooth, but in most part it's thanks to good maintenance, especially of the carburetor and emissions. Note that I wouldn't be able to make the switch to a thinner oil if I hadn't replaced the valve-stem oil seals because the oil consumption would be too high. Before then I was adding about 1 quart every 1,000 miles and with 0W-20 I would have to add about a quart every 250 miles. Now, the oil consumption is almost zero. The next step will be a UOA so that I could see if there is any unexpected wear due to use of thinner oil.
 
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