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I'm not Dell either but I'll offer some simple information since this issue seems to be generally spawn a barrage of FUD. Engineering is always about trade-offs. In the days prior to multi-grade oils automotive engineers were forced to tradeoff reduced lubrication of a heavier oil at cold engine startup to obtain adequate viscosity at engine operating temperature once the oil thinned down. Multi-grade oils were developed to SOLVE THIS UNIVERSAL PROBLEM. There's no such thing as a "single viscosity oil". ALL oils change viscosity with temperature changes. The viscosity of a conventional mineral oil goes DOWN as the temperature of the oil goes up. The viscosity of a multi-grade oil goes UP as the temperature of the oil goes up. And yes a 20W50 is really a 20W base mineral oil with additives (except for synthetics which DO NOT need additives) that change it's physical behavior such that it's viscosity goes up with temperature. So what - viscosity is viscosity. And viscosity is simply a measure of how easily the oil flows - it is not a measure of lubricity. A 20W50 has EXACTLY THE SAME viscosity at 100C as a straight 50W. They are measured using the exact same requirements and procedures. They are not just "equivalent" - they are identical. Just like a 50/50 mix of water and ethyl glycol has a freezing point of about -30F. It's not an "equivalent freezing point - it's THE freezing point. As Sounder notes it is important for an oil to have sufficient viscosity to stay on the parts so it's lubricity can protect the parts. It's also important that the oil not be so viscous when it's cold that the oil pumping system cannot deliver an adequate flow to the parts it's supposed to lubricate. That's the big ADVANTAGE of a multigrade - it pumps better at lower temperatures and has the viscosity at higher temperatures to maintain the oil film necessary to protect engine parts. Any advantage a single grade oil might have as far as not draining away when the motor is not running is slim if any and more than offset by the advantage gained using a multi-grade of getting more oil to running engine parts faster on startup. The addiitives used in multi-grade oils are a problem. Not so much because the "wear out" - you do change your oil regularly don't you - but because the oxidize and leave nasty deposits in the engine. Modern synthetics do not contain additives - they are molecularly different than mineral oils and they do not crud up your engine with deposits. They are a REALLY GOOD oil and are priced accordingly. All that said what's it mean for N's. Well IMHO there's nothing special about these engines. The basics of aiutomotive engoineering apply to them just like a modern OHV engine. Because they are flatheads they do not have as demanding a requirement for oil delivery to the upper end because they don't have one! So the pumping problem of a cold start is not as pronounced and a single grade provides good protection. They also run cold (Hobo says about 160F). So a 10W30 which has a viscosity of 10 at 0C and 30 at 100C is likely to be more like a 20w at operating temp. And similarly a SAE 30W is going to be somewhat higher viscosity - maybe 40W at that temp. So enter Dell's 20W50. On a cold near-zero morning it's somewhere around 20W and when his easy starting 6V N kicks over the oil starts flowing MUCH faster than a SAE 30W which at that temp is near gear oil viscosity and a real load for the N's puny oil pump to suck up. And when that N hits operating temp of 160 (Dell also believes in thermostats) the 20W50 has moved up to say 40W. DOH!
- Do you NEED to run a SAE 30W - no.
- Do you NEED to run a SAE 20W50W - no.
- Do you get better protection from the SAE 20W50 than the SAE 30W in cold climates - I think yes.
YMMV TOH
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