Gene drive systems can lead to the evolution of traits that further enhance the transmission of the driving element. In gene drive, one allele is transmitted to offspring at a higher frequency than the homologous allele. This has a range of consequences, which generally include a reduction in fitness of the carrier of the driving allele, making such systems selfish. The t haplotype is one such driver, found in house mice. It is linked to a reduction in litter size in matings among heterozygous animals, but also to increased lifespan in wild females that carry it. Here, we tested whether carrying the t haplotype was associated with altered resting metabolic rate (RMR). We show that females carrying the t haplotype decrease RMR as they increase in size, compared to wildtype females or males of either genotype. Our study elucidates a plausible mechanism by which a selfish genetic element increases lifespan.