Red Line 15404 SAE 5W40 Full Synthetic Motor Oil - 1 Quart (12 Pack) - Premium Engine Protection for High Performance Cars, Trucks & SUVs

This is the best oil I could find for my specific application. I have a modified and tuned BMW 335d (diesel), that is putting out approximately 600 lb ft of torque at the rear wheels, and just under 375 whp. Given the near 40% increase in torque (and the fact emissions controls were no longer an impediment to the type of lubricants I could use), and with no modification to the lubrication system - I needed to find a suitable oil with a higher HTHS value to protect the lower end components from excessive and accelerated wear - while not going so out of spec in viscosity that I compromised other engine components due to reduced flow from increasing viscosity too much. BMW specifies from 5W30 to 5W40 for the M57 engine. The OEM spec oil is approximately a 3.2-3.4 HTHS viscosity (CP) oil. I searched all available oils in the specified range from every manufacturer for an oil with a notably higher HTHS viscosity and the only company that produces an in-spec oil (5W30-40) with a higher HTHS than OEM spec is Redline. This oil (High Performance 5W40) has a HTHS vis of 4.4 CP, which is a significant increase over the emissions compromised OEM synthetic oil. No other oil manufacturer comes close - not Amsoil, not Motul, not Mobil One, not Royal Purple (not that I would ever use that garbage). In fact, many of the premium brands have a slightly lower HTHS. HTHS is not the biggest selling point either - Redline oils are currently the best oils on the market, with the highest levels of ester. While it’s no longer a complete Group V synthetic (it’s technically a Group IV now based on the proportion of PAO to Ester in the blend - it is of course a true “full synthetic” oil - the ‘blend’ is the combination of synthetic base oils... PAO and Ester), it still has the highest levels of ester in any automotive oil. I also use Redline 0W40 in the winter months. The HTHS is slightly lower (4.0 CP), but still notably higher than OEM. The reduction in vibration during high load and under heavy acceleration is significant - back to stock levels... except accelerating much faster!For note. I’ve been an Amsoil dealer for over 20 years (for personal use - before the preferred customer program came about), but have noticed a disturbing trend of decreasing performance of their products since the founder passed away and his son took over. TBN, NOAK, HTHS, and other important characteristics have all declined to the point their engine oils are really not any better than Mobil One - yet they still charge a premium price. I am not renewing my dealership this year and have converted all of my cars to Redline engine oils and fuel treatments. I still use Amsoil gear and transmission fluids at this point, but will be monitoring their specs for the kind of decline other Amsoil products have suffered.One last note: I contacted Amsoil tech services first when considering my options for a more robust oil. I explained the modifications made to the car and asked what oils they would recommend in the Amsoil product line. To my dismay - they would only recommend their OEM equivalent oil - which actually has a slightly lower HTHS than the BMW spec OEM. They stated they could not make recommendations for modified vehicles. Clearly they do not support the high performance aftermarket any longer. Redline tech services took the information I provided and recommend three of their oils depending on the type of driving. They of course stated that since the car was modified, no company would warranty an engine against oil related failures - but noted Redline Oils have never been the source of any known oil-related engine failure. Redline still supports modders and rodders!