Sorry I didn't answer about oil pressure, the second owner who did not know that it was a former race car , it used 5w50 oil sold the car to me as the pressure was too low and he was afraid by that . As we experienced in France, some K series engine failure due to bad lubrication . As soon I got the Caterham, I filled the car with the right oil and then the pressure raised 1 bar . But what they use 5w50 in a road car : 1) For small trip, if you don't let the car to reach the good temperature ( oil temperature I mean not only water temperature ) before use the car at high rev, the 5w50 is better . 2) I For the valves hydraulic adjustment , during the 5 sec from start , it is better too 3) For emission purpose the 5w50 is better , and for ultimate power and the fuel consumption the 5w50 is better too But for longevity, it is not . I do prefer to warm up the engine With a K series the fuel consumption is ridiculous, so no matter. I do some times trackdays, one of my friend , the president of the French Caterham Club broke his 1800 vvc K series engines due to the 5w50 and he use now a 20w60 Motul 300V Le Mans which to thick from my point of view :-)