Tom NJ
$100 Site Donor 2026
Originally Posted By: JHZR2
Look, we're in violent agreement.
You both make valid points. Keep in mind that there are different kinds of esters, different kinds of varnish, and different operating conditions. In general, “esters” have cleaning properties, but the degree depends on the above variables. A low polarity ester may have a negligible cleaning effect on a hard, baked-on and non-polar varnish, while a high polarity ester may be very effective in cleaning a softer or somewhat polar varnish.
Most esters used as base oils in motor oils are medium and relatively tight in molecular weight, usually between 425 and 670. Likewise for their NPI (non-polarity index), which are usually between 55 and 65. There are some exceptions to this, but they are few. These esters have meaningful solvency properties and should dissolve some varnish, but how much depends on the ester type, ester dosage, and the type of varnish. Generally I would expect them to have a greater effect on sludge than varnish, but significant reduction in varnish is possible. The ester does not need to displace all other chemistries on the metal surface to reduce varnish levels as it can react on the surface of the varnish layer.
Operating conditions also play a role, as do other chemistries in the formulation. Significant cleaning is often observed in high temperature industrial applications with high ester content oils, but the complexity of the chemistry in motor oils makes it difficult to isolate and measure the specific effect of an ester at lower dosages. And since esters are out of favor among the majors due to cost, I am not aware of any published studies being conducted to measure ester cleaning effects in modern engines. I believe it is reasonable to deduce that the solvency contributed by the ester has some cleaning effect in automotive engines, but I would not venture to quantify it, and it would vary by engine and oil. If I had severe varnish I would be inclined to use a cocktail of powerful solvents such as Kreen, but I also believe that the use of a high ester oil such as RL would also give improvement over time.
Tom NJ
Look, we're in violent agreement.
You both make valid points. Keep in mind that there are different kinds of esters, different kinds of varnish, and different operating conditions. In general, “esters” have cleaning properties, but the degree depends on the above variables. A low polarity ester may have a negligible cleaning effect on a hard, baked-on and non-polar varnish, while a high polarity ester may be very effective in cleaning a softer or somewhat polar varnish.
Most esters used as base oils in motor oils are medium and relatively tight in molecular weight, usually between 425 and 670. Likewise for their NPI (non-polarity index), which are usually between 55 and 65. There are some exceptions to this, but they are few. These esters have meaningful solvency properties and should dissolve some varnish, but how much depends on the ester type, ester dosage, and the type of varnish. Generally I would expect them to have a greater effect on sludge than varnish, but significant reduction in varnish is possible. The ester does not need to displace all other chemistries on the metal surface to reduce varnish levels as it can react on the surface of the varnish layer.
Operating conditions also play a role, as do other chemistries in the formulation. Significant cleaning is often observed in high temperature industrial applications with high ester content oils, but the complexity of the chemistry in motor oils makes it difficult to isolate and measure the specific effect of an ester at lower dosages. And since esters are out of favor among the majors due to cost, I am not aware of any published studies being conducted to measure ester cleaning effects in modern engines. I believe it is reasonable to deduce that the solvency contributed by the ester has some cleaning effect in automotive engines, but I would not venture to quantify it, and it would vary by engine and oil. If I had severe varnish I would be inclined to use a cocktail of powerful solvents such as Kreen, but I also believe that the use of a high ester oil such as RL would also give improvement over time.
Tom NJ
