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#21 | |
![]() ![]() Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,493
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Again, the issue is direct vs. indirect "testing". Direct testing on the 1G LT5 is cost prohibitive, especially considering the lack of new or substitute parts. And, it takes significant runtime/stress testing to gather evidence enough to make any scientific, definitive conclusion(s). So, in absents of direct testing, we're relegated/obliged to accept INDIRECT test data results gathered with other (engines) operating with identical or at least practically close conditions. My point is, the data for making a direct comparison(s) and much less predictions between results of this latest (Mobil 1) oil and that of products having considerably more real runtime data on actual 1G LT5s rests solely on a manufacture's reputation and little if anything else - comparatively speaking. EXAMPLE: Various antifreeze makers provided a revolutionary coolant (referred to commonly as DEXCOOL; a coolant improvement over the traditional (GREEN) silicon base coolant which "Dex" superseded. But, if one were to replace their GREEN stuff with DEXCOOL solely on the assumption that the "DEX" was made by a reputable company and therefore suitable for their LT5, they were in for a very expensive mistake. Companies like Mobil 1 make a variety of products for various applications. But, applications differ, and one size does not always fit all!Your mileage may vary....
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Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry |
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#22 | ||
![]() ![]() Join Date: Aug 2009
Location: South Dakota/California
Posts: 3,794
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Going from a 4,000 rpm to over a 7,000 rpm engine is a BIG factor in Cam Pressure and wear. I also know from an experience that the cam tips are not parallel with the Lifter surface on the LT5 engine. (Cam Tip being the high "edge" of the Cam that gives the Lifter maximum compression). An Aberration in Cam Wear The localized pressure on the lifter must be very difficult to determine in that case.... The Cam Wear on the tips can be seen on the Cams pictured below. ![]() ![]() I assume the cam tip being tilted and off center on the Lifter surface keeps the lifter rotating. The lifter rotating under the cam acts like a rolling intersection (not purely frictional). [B]The surface of the Lifter is moving vertically and horizontaly as the Cam Tip slides/rolls across the Lifter. (It is hard to imagine this happening up to 60 times a second). Redline (maximum safe operational engine speed) is a BIG factor on ZDDP issues..... Redline for L98 is 5,500 rpm. Redline for LT5 is 7,200 rpm. Mobile-1 for racing engines (high rpm) shows much higher ZDDP ![]() Quote:
A little more detail on Oil/Zinc/Cam Wear from Hib Halverson........ ![]() ![]() Oil/Zinc/Cam Wear Part 1 Oil/Zinc/Cam Wear Part 2
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Left Clickable links ![]() -Solutions- LT5 Modifications/Rebuild Tricks Low Mileage ZR-1 Restoration 1990 Corvette (L98) Modifications LT5 Eliminated Systems LT5 Added Systems LT5/ZR-1 Fluids 1995 LT5 SPECIFIC TOP END REBUILD TRICKS Last edited by Dynomite; 10-02-2022 at 03:34 PM. |
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#23 |
![]() Join Date: Jun 2013
Location: PA
Posts: 879
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https://www.mobil.com/lubricants/-/m...pecs-guide.pdf
Notice on every Mobile 1 oil with API certification the recommendation states "Vehicles that require XW‐ XX." There is not one spot in their product guide that recommends using a viscosity not originally recommended by the manufacturer. Notice the zinc and phosphorus content on the racing oils... Again, this whole topic is grayed significantly by the regulations governing oil, fuel economy, emissions equipment, etc. Aviation oil still has or recommends as an additive, Tris(methylphenyl)phosphate (Tritricresyl phosphate). Long banned in automotive oils and with relatively high toxicity, but in a market that is widely unregulated. A market that suffered many of the same issues listed in Hib's articles, such as the ceasing of lifter production by Eaton who's secret sauce recipe for lifters supplied aviation for a long time. Another good read for those who really want to get into the weeds: https://www.mdpi.com/2075-4442/1/4/132/htm |
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#24 | |
![]() Join Date: Jul 2017
Location: West Chester, PA
Posts: 378
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Interesting stuff for the engineering types out there. The paper gives a sense of the complexities if tribology, and the difficulty in balancing advantages and disadvantages of various additives for oil manufacturers. My takeaways: motor oils are not all created equal; stick with what is known to work unless there's good reason not to; the devil is in the details. Appreciate the reads! ![]()
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1990 Black/Black ZR-1 #1155 1993 White/Red coupe (Regrettably sold) ![]() |
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#25 | |
![]() Join Date: Jul 2017
Location: West Chester, PA
Posts: 378
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Thanks for the pointers to these articles. I imagine this is about as detailed a history as you are going to find anywhere on the topic. Early in the Part 1 article, it is stated that the LT-5 having flat tappets is "... only peripherally related to this wear issue, because it had overhead cams and direct acting, bucket-type flat tappets." It would seem to imply that the LT-5 operating conditions are less severe, but I may be reading to much into that statement. I'd be interested to know what drove the choice of ZDDP content for the LT-5 and whether it's valve train design is a more or less (or neither) severe case in terms of valve train loading and wear compared to older flat tappet OHV engine designs. Also, if anyone knows, whether the recommended oil for the LT-5 changed at all between the different model years?
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1990 Black/Black ZR-1 #1155 1993 White/Red coupe (Regrettably sold) ![]() |
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#26 | |
![]() Join Date: Jun 2013
Location: PA
Posts: 879
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However, emissions equipment life drove the ZDDP content for all API approved engine oils. Zinc deposits can reduce catalytic converter life. Interestingly, I haven't found any great articles on how much zinc reduces the catalyst life by how much. |
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#27 | |
![]() ![]() Join Date: Aug 2009
Location: South Dakota/California
Posts: 3,794
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Redline (maximum safe operational engine speed) is a BIG factor on ZDDP requirement issues.....
Redline for L98 is 5,500 rpm. Redline for LT5 is 7,200 rpm. Mobile-1 for racing engines (high rpm) shows much higher ZDDP ![]() Quote:
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Left Clickable links ![]() -Solutions- LT5 Modifications/Rebuild Tricks Low Mileage ZR-1 Restoration 1990 Corvette (L98) Modifications LT5 Eliminated Systems LT5 Added Systems LT5/ZR-1 Fluids 1995 LT5 SPECIFIC TOP END REBUILD TRICKS Last edited by Dynomite; 10-02-2022 at 03:35 PM. |
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