“I've been using Total semi-synthetic 10w40 for some years in my 1974 Citroën D Super 5 (DS21 engine) rather than the recommended 20w50 mineral oil. I noticed a number of improvements : cooler running, easier starting, better fuel economy, a quieter engine and much less oil used between changes (at 3000 miles). But after a number of hot summer drives in France and Italy : frequently 40º+, Ithought I would try a fully synthetic oil. Having considered a 10w60 I saw the Miller's on the Opie website. It does everything the Total does but is much quieter at speed. I changed the oil 3400 miles after setting off for the Beaujolais and the Pyrenees this August. It came out still translucent with a healthy colour. The magnetic drain plug was clean. I would be confident in pushing the oil change interval to 4000 miles. For winter I'm using 10w40 semi-synthetic again - when starting, the cold engine spins so much faster on the thinner oil. But next summer it will be the fully synthetic 20w50 again. I have already bought another 5 litres!”
