What's the best oil for use in my 240?
OK, after working for the past 2 and a half years at a car dealership and seeing the
various effects of oil on engines, I've come up with 2 main opinions:
1. Use the good stuff (i.e. Mobil 1)
2. Change it a lot (every 3 mos./3000 miles...regardless of what the Nissan Manual says)
The best oil I've found for the 240 is Mobil 1 0W-40. Simply awesome. I was using the
15W-50 before, but the car felt sluggish and the valves had a nasty habit of tapping until
the engine was VERY warm. The lower weight oil worked wonders. Revs faster and smoother
and no more valve tap!!
Oh, and don't mess with additives...you should see what they do to engine internals...
Eric Johnson
Email: [email protected]
Mobil-1 Information
You might like to post this email to the 240SX list, I think it might be of interest to the members, in view of some recent discussions about Synthetic, Mobil 1 etc. .... Tref sent it to me, he subscribes to the TVR list in the UK and that's where this came from.
Cheers
Neville
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Following the recent (ish) debate about Mobil 1 prices in France being (5w50) versus (0w40) here, I've managed to get a great explanation from a guy at Mobil .....
5W-50 fully synthetic was a simple blend of PAO (Polyalphaolefin ) synthetic and complementary additives. In its time it was the best oil on the market. However, our main client base technically demanded advancement in our offer. Mobil continually develop products and we have now engineered a formulation of different synthetic base oils further enhance our product.
Areas of concern were fuel economy, product durability and emissions. We use two types of the PAO and an ester as used in jet engine lubrication. This results in a product that is more stable at high temperatures, so it lasts longer and this has enabled us to lower the viscosity to 0W40.
TVR have approved this oil for use in their engine, in fact the new speed 12 and 6 cylinder unit were designed around it!
0W40 is fully miscible with the older 5W-50 but the higher viscosity would not benefit you for fuel economy. However I doubt weather this is a burning issue to you with this type of vehicle! The 0W-40 will get around the engine quickly on startup so there is an advantage here and it gives improved antiwear performance so yes there is an advantage in using the new formulation. Maybe you use the 5W-50 for topup as this will have very little effect on the main charge during the service interval.
Alternatively use it on older vehicle where higher viscosity is desired.
Mike Frost
Auto Tech Mgr, Mobil
More Than You Ever Wanted to Know About Motor Oil
By Ed Hackett <[email protected]>
Edits: v1.0 First there was 1.0. Before that there was darkness.
v1.1 Change in description of viscosity.
v1.2 Updated info on AMSOIL (courtesy of Morgan McArthur <[email protected]>)
Choosing the best motor oil is a topic that comes up frequently in discussions between
motoheads, whether they are talking about motorcycles or cars. The following article is
intended to help you make a choice based on more than the advertising hype.
Oil companies provide data on their oils most often referred to as "typical
inspection data". This is an average of the actual physical and a few common chemical
properties of their oils. This information is available to the public through their
distributors or by writing or calling the company directly. I have compiled a list of the
most popular, premium oils so that a ready comparison can be made. If your favorite oil is
not on the list get the data from the distributor and use what I have as a data base.
This article is going to look at six of the most important properties of a motor oil
readily available to the public: viscosity, viscosity index (VI), flash point, pour point,
% sulfated ash, and % zinc.
Viscosity is a measure of the "flowability" of an oil. More specifically, it is
the property of an oil to develop and maintain a certain amount of shearing stress
dependent on flow, and then to offer continued resistance to flow. Thicker oils generally
have a higher viscosity, and thinner oils a lower viscosity. This is the most important
property for an engine. An oil with too low a viscosity can shear and lose film strength
at high temperatures. An oil with too high a viscosity may not pump to the proper parts at
low temperatures and the film may tear at high rpm.
The weights given on oils are arbitrary numbers assigned by the S.A.E. (Society of
Automotive Engineers). These numbers correspond to "real" viscosity, as measured
by several accepted techniques. These measurements are taken at specific temperatures.
Oils that fall into a certain range are designated 5, 10, 20, 30, 40, 50 by the S.A.E. The
W means the oil meets specifications for viscosity at 0 F and is therefore suitable for
Winter use.
Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W),
which prevent the oil from thinning as much as it warms up. At cold temperatures the
polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil
warms up the polymers begin to unwind into long chains that prevent the oil from thinning
as much as it normally would. The result is that at 100 degrees C the oil has thinned only
as much as the higher viscosity number indicates. Another way of looking at multi-vis oils
is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would
when hot.
Multi viscosity oils are one of the great improvements in oils, but they should be chosen
wisely. Always use a multi grade with the narrowest span of viscosity that is appropriate
for the temperatures you are going to encounter. In the winter base your decision on the
lowest temperature you will encounter, in the summer, the highest temperature you expect.
The polymers can shear and burn forming deposits that can cause ring sticking and other
problems. 10W-40 and 5W-30 require a lot of polymers (synthetics excluded) to achieve that
range. This has caused problems in diesel engines, but fewer polymers are better for all
engines. The wide viscosity range oils, in general, are more prone to viscosity and
thermal breakdown due to the high polymer content. It is the oil that lubricates, not the
additives. Oils that can do their job with the fewest additives are the best.
Very few manufactures recommend 10W-40 any more, and some threaten to void warranties if
it is used. It was not included in this article for that reason. 20W-50 is the same 30
point spread, but because it starts with a heavier base it requires less viscosity index
improvers (polymers) to do the job. AMSOIL can formulate their 10W-30 and 15W-40 with no
viscosity index improvers but uses some in the 10W-40 and 5W-30. Mobil 1 uses no viscosity
improvers in their 5W-30, and I assume the new 10W-30. Follow your manufacturer's
recommendations as to which weights are appropriate for your vehicle.
Viscosity Index is an empirical number indicating the rate of change in viscosity of an
oil within a given temperature range. Higher numbers indicate a low change, lower numbers
indicate a relatively large change. The higher the number the better. This is one major
property of an oil that keeps your bearings happy. These numbers can only be compared
within a viscosity range. It is not an indication of how well the oil resists thermal
breakdown.
Flash point is the temperature at which an oil gives off vapors that can be ignited with a
flame held over the oil. The lower the flash point the greater tendency for the oil to
suffer vaporization loss at high temperatures and to burn off on hot cylinder walls and
pistons. The flash point can be an indicator of the quality of the base stock used. The
higher the flash point the better. 400 F is the minimum to prevent possible high
consumption. Flash point is in degrees F.
Pour point is 5 degrees F above the point at which a chilled oil shows no movement at the
surface for 5 seconds when inclined. This measurement is especially important for oils
used in the winter. A borderline pumping temperature is given by some manufacturers. This
is the temperature at which the oil will pump and maintain adequate oil pressure. This was
not given by a lot of the manufacturers, but seems to be about 20 degrees F above the pour
point. The lower the pour point the better. Pour point is in degrees F.
% sulfated ash is how much solid material is left when the oil burns. A high ash
content will tend to form more sludge and deposits in the engine. Low ash content also
seems to promote long valve life. Look for oils with a low ash content.
% zinc is the amount of zinc used as an extreme pressure, anti-wear additive. The zinc is
only used when there is actual metal to metal contact in the engine. Hopefully the oil
will do its job and this will rarely occur, but if it does, the zinc compounds react with
the metal to prevent scuffing and wear. A level of .11% is enough to protect an automobile
engine for the extended oil drain interval, under normal use. Those of you with high
revving, air cooled motorcycles or turbo charged cars or bikes might want to look at the
oils with the higher zinc content. More doesn't give you better protection, it gives you
longer protection if the rate of metal to metal contact is abnormally high. High zinc
content can lead to deposit formation and plug fouling.
Brand VI Flash Pour %ash %zinc
20W-50
AMSOIL (old) 136 482 -38 <.5 ---
AMSOIL (new) 157 507 -44 --- ---
Castrol GTX 122 440 -15 .85 .12
Exxon High Performance 119 419 -13 .70 .11
Havoline Formula 3 125 465 -30 1.0 ---
Kendall GT-1 129 390 -25 1.0 .16
Pennzoil GT Perf. 120 460 -10 .9 ---
Quaker State Dlx. 155 430 -25 .9 ---
Red Line 150 503 -49 --- ---
Shell Truck Guard 130 450 -15 1.0 .15
Spectro Golden 4 174 440 -35 --- .15
Spectro Golden M.G. 174 440 -35 --- .13
Unocal 121 432 -11 .74 .12
Valvoline All Climate 125 430 -10 1.0 .11
Valvoline Turbo 140 440 -10 .99 .13
Valvoline Race 140 425 -10 1.2 .20
Valvoline Synthetic 146 465 -40 <1.5 .12
20W-40
AMSOIL 124 500 -49 --- ---
Castrol Multi-Grade 110 440 -15 .85 .12
Quaker State 121 415 -15 .9 ---
15W-50
Chevron 204 415 -18 .96 .11
Mobil 1 170 470 -55 --- ---
Mystic JT8 144 420 -20 1.7 .15
Red Line 152 503 -49 --- ---
5W-50
Castrol Syntec 180 437 -45 1.2 .10
Quaker State Synquest 173 457 -76 --- ---
Pennzoil Performax 176 --- -69 --- ---
5W-40
Havoline 170 450 -40 1.4 ---
15W-40
AMSOIL (old) 135 460 -38 <.5 ---
AMSOIL (new) 164 462 -49 --- ---
Castrol 134 415 -15 1.3 .14
Chevron Delo 400 136 421 -27 1.0 ---
Exxon XD3 --- 417 -11 .9 .14
Exxon XD3 Extra 135 399 -11 .95 .13
Kendall GT-1 135 410 -25 1.0 .16
Mystic JT8 142 440 -20 1.7 .15
Red Line 149 495 -40 --- ---
Shell Rotella w/XLA 146 410 -25 1.0 .13
Valvoline All Fleet 140 --- -10 1.0 .15
Valvoline Turbo 140 420 -10 .99 .13
10W-30
AMSOIL (old) 142 480 -70 <.5 ---
AMSOIL (new) 162 520 -76 --- ---
Castrol GTX 140 415 -33 .85 .12
Chevron Supreme 150 401 -26 .96 .11
Exxon Superflo Hi Perf 135 392 -22 .70 .11
Exxon Superflo Supreme 133 400 -31 .85 .13
Havoline Formula 3 139 430 -30 1.0 ---
Kendall GT-1 139 390 -25 1.0 .16
Mobil 1 160 450 -65 --- ---
Pennzoil PLZ Turbo 140 410 -27 1.0 ---
Quaker State 156 410 -30 .9 ---
Red Line 139 475 -40 --- ---
Shell Fire and Ice 155 410 -35 .9 .12
Shell Super 2000 155 410 -35 1.0 .13
Shell Truck Guard 155 405 -35 1.0 .15
Spectro Golden M.G. 175 405 -40 --- ---
Unocal Super 153 428 -33 .92 .12
Valvoline All Climate 130 410 -26 1.0 .11
Valvoline Turbo 135 410 -26 .99 .13
Valvoline Race 130 410 -26 1.2 .20
Valvoline Synthetic 140 450 -40 <1.5 .12
5W-30
AMSOIL (old) 168 480 -76 <.5 ---
AMSOIL (new) 186 464 -76 --- ---
Castrol GTX 156 400 -35 .80 .12
Chevron Supreme 202? 354 -46 .96 .11
Chevron Supreme Synt. 165 446 -72 1.1 .12
Exxon Superflow HP 148 392 -22 .70 .11
Havoline Formula 3 158 420 -40 1.0 ---
Mobil 1 165 445 -65 --- ---
Mystic JT8 161 390 -25 .95 .1
Quaker State 165 405 -35 .9 ---
Red Line 151 455 -49 --- ---
Shell Fire and Ice 167 405 -35 .9 .12
Unocal 151 414 -33 .81 .12
Valvoline All Climate 135 405 -40 1.0 .11
Valvoline Turbo 158 405 -40 .99 .13
Valvoline Synthetic 160 435 -40 <1.5 .12
All of the oils above meet current SG/CD ratings and all vehicle manufacture's warranty
requirements in the proper viscosity. All are "good enough", but those with the
better numbers are icing on the cake.
The synthetics offer the only truly significant differences, due to their superior high
temperature oxidation resistance, high film strength, very low tendency to form deposits,
stable viscosity base, and low temperature flow characteristics. Synthetics are superior
lubricants compared to traditional petroleum oils. You will have to decide if their high
cost is justified in your application.
The extended oil drain intervals given by the vehicle manufacturers (typically 7500 miles)
and synthetic oil companies (up to 25,000 miles) are for what is called normal service.
Normal service is defined as the engine at normal operating temperature, at highway
speeds, and in a dust free environment. Stop and go, city driving, trips of less than 10
miles, or extreme heat or cold puts the oil change interval into the severe service
category, which is 3000 miles for most vehicles. Synthetics can be run two to three times
the mileage of petroleum oils with no problems. They do not react to combustion and
combustion by-products to the extent
that the dead dinosaur juice does. The longer drain intervals possible help take the bite
out of the higher cost of the synthetics. If your car or bike is still under warranty you
will have to stick to the recommended drain intervals. These are set for petroleum oils
and the manufacturers make no official allowance for the use of synthetics.
Oil additives should not be used. The oil companies have gone to great lengths to develop
an additive package that meets the vehicle's requirements. Some of these additives are
synergistic, that is the effect of two additives together is greater than the effect of
each acting separately. If you add anything to the oil you may upset this balance and
prevent the oil from performing to specification.
The numbers above are not, by any means, all there is to determining what makes a top
quality oil. The exact base stock used, the type, quality, and quantity of additives used
are very important. The given data combined with the manufacturer's claims, your personal
experience, and the reputation of the oil among others who use it should help you make an
informed choice.