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#438 of 4534 Re: Bobby [z71bill #436] by bmwbobby Apr 25, 2004 (5:53 pm)
Replying to: z71bill (Apr 25, 2004 8:38 am) There has been a lot of discussions about all this in technical lubrication journals. The myths are not mine but are more likely yours. There is ridiculous talk about engines being changed to suit 5W-20 oils but this is not true. Main bearings, big and small end journal bearings, etc, have similar clearances as they've always had on this type of small high specific output engine. Of course camshafts run with essentially no clerarance on these and all cars and are considered to have what is known as boundary type lubrication (not elastohydrodynamic as in the bearings. It is well known by lubication engineers that camshafts would be best protected (other than during startup) with a 50 weight oil but that is too viscous for the other engine parts and would lead to poor fuel mileage. The exact same Honda and Ford engines that have not changed at all that had recommended 5W-30 and even allowed 10W-40 in hot weather now suddenly require 5W-20 all season long? This is simply a CAFE issue. Anyway, lubrication viscosity preference is determined by three factors, load amount; interfacial velocity; and temperature. Higher loads demand higher viscosity; higher speeds demand lower viscosity (consider hydroplaning as a form of hydrodynamic lubrication), and higher temps demand higher viscosity. Be aware that each of these factors vary wildly in your engine, piston speed is low near the top and bottom of the stroke, cam turns at half of crankshaft speed; rod journal bearings have about 3 times more load than the mains. What is not a myth is that oil sump temperatures have gone up a ton over the last 25 years due to the much much higher specific outputs (Hp/CID)and due to runnning much less air under the vehicles ie lower ground clearance and air dams, new air cover plates, like the one on your Mazda 3. On older cars like a 73 Plymouth valiant, about 20% of the total engine cooling was done by air circulating under the hood, but this isn't too good for aerodynamics and those days are over.   Like any heat engine (gasoline is called the Otto cycle), output and efficiency go up with operating temperature. This is true for Brayton cycle engines too (that's a gas turbine or jet engine), Diesel engines, etc. As a modern jet engine runs a firing temperatue about 500F hotter than they did 25 years ago, your modern car runs much hotter too.   http://www.machinerylubrication.com/article_detail.asp?articleid=- 365&relatedbookgroup=Lubrication   First of all, when it is hot out, especially if you are in city type traffic for long periods of time, your water temperatures will go up significantly as compared to cold days doing highway driving. When water temperatures go up, so do metal and lubricant sump temperatures. Lubricant sump temperatures can be in the 240F range. Your 5W-20 oil has a viscosity approaching just 5 centistokes and will also be quite volatile with its short chain molecules. Your cams will be totally dependent on the anti-adhesive wear additives it has like ZDP which I hear they are loading up 5W-20 oils with to the brim. Anyway, I hope you're getting the point.   ANyway, do consider that the 30 weight designation refers to a specified viscosity range at 212F. At lower temperatures, a 5W-30 behaves just like the 5W-20 and doesn't add any extra film thickness until you need it, when it gets really hot. If you'd like anymore information documenting the changes in engine and oil sump tempratures over the years, do ask. If you are doubting that they can be affected by ambient temperatures, especially in extremes like 15F vs 95F, then you need more help than I can render.   Bobby
#439 of 4534 3M paint-protection film works great. by mazdafun Apr 26, 2004 (4:25 am)
I've only got the headlamp kit on my '99 Pro LX, but my wife's '03 P5 has the full front-end treatment (bumper, hood, fenders), under the door handles, side mirrors, top of the rear bumper and all front lights (including fogs). So far, only one region that has been marred by a large rock that hit it (good thing it was there; that probably would've left a huge scratch in the paint).   We put it on ourselves (we bought pre-cut kits). Other than the fenders, rear bumper and the lights, it was a big pain to install (it's definitely a 2-person job on the larger pieces). I'd pay for a professional to do it the next time.
#440 of 4534 Bobby by z71bill Apr 26, 2004 (5:42 am)
Kind of a long post -   So you think you know more then the people that designed and built your car? I am sure that Mazda uses high school drop outs to decide what kind of oil to use in their engines! Or maybe they ask the guy at Jiffy Lube what he thinks is best!   Your assumption that you need "extra film thickness" is where you get off track. That is the myth.   Just why do you think that this is required? Or better?   While at a lubrication seminar I took several years ago the instructor (PHD chemical engineering with 30+ years real world experience) explained it this way.   You are at the beach and decide to run 1 mile - which is easier?   1. Running in the water up to your knees (heavy oil film) 2. Running on the wet sand (light oil film) 3. Running on the dry loose sand (no oil film)   Your comment on CAFE is mostly true - but also helps to prove my point (thank you). The 5W-20 provides the best MPG - do you really think that would be true if it was not providing proper (could argue better) lubrication?   Again - the 5W-30 will not hurt your engine - but it will also not provide any real benefit and may give you big problems if you have a major engine failure while under warranty. Mazda could elect to not honor the warranty - because you did not do PROPER MAINTENANCE.   As far as sump temperatures being hotter with outside temperatures at 95 degrees VS 15. I would agree with that - but so what. The 5W-20 will still provide proper lubrication.   The bottom line IMO - you are better off using the manufacturer's requirements. Replies to this message: bmwbobby (Apr 26, 2004 6:12 am) bmwbobby (Apr 26, 2004 6:27 am)
#441 of 4534 Re: Bobby [z71bill #440] by bmwbobby Apr 26, 2004 (6:12 am)
Replying to: z71bill (Apr 26, 2004 5:42 am) You're missing the point amigo and need to read a little more carefully. I didn't say you need extra film thickness, what I was saying is that in some parts of the engine, even with 30w oil, you don't really have any thick film lubrication to begin with (ie, camshafts) and you may be close to running without a film in bearings too if you're inlet viscosity is too low and your load is high. You're right about thick film lubrication, once you've got it, you don't need to get much thicker but as temperatures and loads go up, you may not have it anymore!!! Have you ever observed a viscosity versus temeperature graph for a motor oil? Why do race vehicles have oil coolers amigo? Do you think you know more than they do and that they should be using 20 Weight oil without oil coolers?. On cool days with short trips, 5W-20 is too thick, you could survive with even thinner oil because the oil and motor don't get very hot. It all depends on the real situation locally in the engine amigo, oil inlet temperature to the load zone, local metal temperature, interface speed, and load. If you were racing the car in hot weather, you'd be an assclown to use 5W-20. In fact, there will surely be versions of this car raced in the SCCA and other semi-stock motorsport events and I guaran-damn-tee yo they will be using heavier oils with high temperature, probably of the 40 Weight variety or higher. This is because of higher temperatures and loads. Is that so difficult to understand now? At 6500 RPM, your radial loads on the bearings are extreme!!!!    As far as the legalities are concerned, you are again most uneducated, read this FAQ from a motor oil supplier:   Question: My owners manual specifies 5W-20 oil. Do I really need to use 5W-20 oil and why did my 2000 model year vehicle require a 5W-30 oil, while the exact same engine in my 2001, 2002 and newer engines "requires" a 5W-20 oil?   Answer: You do not need to use a 5W-20 oil. Do not let your dealer scare you by telling you that you have to use it for your warranty. That is a tactic that some dealerships use to scare customers. Once you know the facts and the Federal Magnusson Moss Act law you will be much better informed to protect your rights and use the type of oil you want to use.   The main reason 5W-20 was specified for your engine is to increase the CAFE (Corporate Average Fuel Economy) reported to the Federal Government. CAFE is the combined average fuel economy of all of a vehicle manufacturers product line. Minimum CAFE levels are specified by the Federal Government. In order for a vehicle manufacturer to continue selling profitable large trucks and SUV's, which typically have poor fuel mileage ratings, as compared to smaller cars, and still meet mandated CAFE requirements, they must also sell enough of the smaller cars which have much better fuel economy ratings to offset the poor fuel economy ratings of the larger vehicles. For model year 2001, the change to a 5W-20 oil will allow Ford and Honda's overall CAFE to increase by a very small amount, typically in the tenths of a mile per gallon range. 5W-20 oil is a lighter viscosity than a 5W-30 oil and therefore has less internal engine frictional losses, or less drag on the crankshaft, pistons and valvetrain, which in turn promotes increased fuel economy. This increased fuel economy is virtually undetectable to the average motorist without the use of specialized engine monitoring and testing equipment under strictly controlled test track driving when compared to a 5W-30, 10W-30 or a 0W-30 viscosity motor oil.   Question: Could using a 5W-30, 10W-30, 0W-30 or even a 10W-40 or 20W-50, oil in my vehicle which specifies a 5W-20 oil void my new car warranty?   Answer: Absolutely not. Vehicle manufacturers only recommend using motor oils meeting certain viscosity grades and American Petroleum Institute service requirements. Whether a motor oil is a 5W-20, 5W-30, 10W-30, 0W-30, 10W-40 or 20W-50 (for racing and high performance applications in, for example, a Cobra R Mustang) or even a synthetic vs. a petroleum based oil will not affect warranty coverage. The manufacturer is required by Federal Law to cover all equipment failures it would normally cover as long as the oil meets API service requirements and specifications and was not the cause of failure. In addition, the Federally mandated Magnuson - Moss Act states that a manufacturer may not require a specific brand or type of aftermarket product unless it is provided free of charge. If your dealership continues to tell you that you must use 5W-20 motor oil and or/ a specific brand of 5W-20 motor oil, then ask them to put it in writing. Their position is inaccurate, and, in fact violates existing law.*
#442 of 4534 Re: Bobby [z71bill #440] by bmwbobby Apr 26, 2004 (6:27 am)
Replying to: z71bill (Apr 26, 2004 5:42 am) Rad this amigo: http://www.noria.com/learning_center/category_article.asp?article- id=518&relatedbookgroup=Maintenance   Here is an excerpt: "Any abrasive particles equal to or larger than the oil film thickness will cause wear. Filters are necessary to keep contaminants small. The other side of the equation is oil film thickness. Thicker oil films can accommodate larger contaminants.   "Temperature has a big effect on viscosity and film thickness. As a point of reference, one SAE grade increase in viscosity is necessary to overcome the influence of a 20°F increase in engine temperature. At a given reference point, there is approximately a 20°F. difference between viscosity grades SAE 30, 40 and 50. SAE 20 is somewhat closer to 30 than the other jumps, because SAE 30 must be 30°F higher than SAE 20 to be roughly the equivalent viscosity.   In other words, an SAE 20 at 190°F is about the same kinematic viscosity as an SAE 30 at 220°F, which is about the same viscosity as an SAE 40 at 240°F. This approximation works well in the 190°F to 260°F temperature range. One might be surprised at the slight amount of difference between straight viscosity vs. multiviscosity oils with the same back number (for example, SAE 30, SAE 5W-30, and SAE 10W-30)."   "Any abrasive particles equal to or larger than the oil film thickness will cause wear. Filters are necessary to keep contaminants small. The other side of the equation is oil film thickness. Thicker oil films can accommodate larger contaminants.   Temperature has a big effect on viscosity and film thickness. As a point of reference, one SAE grade increase in viscosity is necessary to overcome the influence of a 20°F increase in engine temperature. At a given reference point, there is approximately a 20°F. difference between viscosity grades SAE 30, 40 and 50. SAE 20 is somewhat closer to 30 than the other jumps, because SAE 30 must be 30°F higher than SAE 20 to be roughly the equivalent viscosity.   In other words, an SAE 20 at 190°F is about the same kinematic viscosity as an SAE 30 at 220°F, which is about the same viscosity as an SAE 40 at 240°F. This approximation works well in the 190°F to 260°F temperature range. One might be surprised at the slight amount of difference between straight viscosity vs. multiviscosity oils with the same back number (for example, SAE 30, SAE 5W-30, and SAE 10W-30)."    Did your PhD buddy tell you that having a film thickness bigger than the size of wear particles is most helpful.   More quotes "Antiwear additives are important in the absence of a hydrodynamic film, such as in the valve train. The antiwear additives are activated by frictional heat, which causes them to react with the hot surface and form a chemical barrier to wear.   Short-term Thinking As wear increases, the efficiency of an engine declines. Valve train wear slightly changes valve timing and movement. Ring and liner wear affect compression. The wear hurts fuel efficiency and power output by an imperceptible amount at first, but then the difference in fuel economy between an SAE 10W-30 and SAE 5W-20 is hardly noticeable. Efficiency continues to decline as wear progresses. Perhaps optimizing wear protection is the way to reduce fuel consumption over the life of the engine."   Educate yourself about the basics of lubrication before you go spouting off on these forums like an assclown. If 20F is significant, what about 40F or 50F? Temperature is everything in this game amigo. Why do you think I mentioned higher high temperature viscosities for higher temperature engine use?   Bobby
#443 of 4534 by gandrigo Apr 26, 2004 (7:06 am)
Thanks heavens for the profound and educated opinions of bmwbobby. comparing high load and temp racetrack situations to those encountered by people such as me on the street does little to prove a point. technically, the 10W30 oil will provide better protection at higher temp (beyond regular operating parameters) than the 5W20, but that does not render the 5W20 inadequate. the specified grade will do the job under anything close to extreme conditions, and that includes hot and cold weather. At normal operating temperature, the 5W30 will not act like a 5W20, and yes that is a fact. The oil pump and passageways were designed to optimize efficiency for a given weight oil within a specific operating range. A pump will not deliver the same volume of different viscosity fluids at a given temperature. how will this affect wear? I am nowhere near as qualified as the individuals who designed and tested this motor, and I would wager few people here are. We are all entitled to personal opinions.
#444 of 4534 Interesting oil debate.... by Apr 26, 2004 (8:05 am)
...yet off topic. You can trot over to Engine Oil - A slippery subject in M&R to continue.

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